# Lux Readings - T8x2 Diamond Plate Fixture



## Hoppy (Dec 24, 2005)

Are those readings in lux? Does the reading need to be multiplied by 10? (high range on meter) The readings are much too low, but if multiplied by 10 are about what I would expect. I plotted the results and the data look very good, except for possibly being off by a factor of 10

EDIT: It can't be off by a factor of 10 either, more like a factor of 5. If it was off by 10 this light would be giving more PAR than a Hagen GLO two bulb T5HO light, and I find that hard to believe. One thing that would help would be a few measurements with only one bulb installed. Something is wrong here.


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## sowNreap (Jun 10, 2012)

Hoppy said:


> Are those readings in lux? Does the reading need to be multiplied by 10? (high range on meter) The readings are much too low, but if multiplied by 10 are about what I would expect. I plotted the results and the data look very good, except for possibly being off by a factor of 10
> 
> EDIT: It can't be off by a factor of 10 either, more like a factor of 5. If it was off by 10 this light would be giving more PAR than a Hagen GLO two bulb T5HO light, and I find that hard to believe. One thing that would help would be a few measurements with only one bulb installed. Something is wrong here.


Yes readings are Lux. And after I thought about it I used the 20000 scale (2nd range says x10) so I assume it does need to be multiplied by something. 

I'll try the readings with one bulb to see what I get. 

Anything else I should do while I'm at it?

EDIT: I tried the reading at x1 lowest scale but it only had a "1" on the display and wouldn't read anything.


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## Hoppy (Dec 24, 2005)

sowNreap said:


> Yes readings are Lux. And after I thought about it I used the 20000 scale (2nd range says x10) so I assume it does need to be multiplied by something.
> 
> I'll try the readings with one bulb to see what I get.
> 
> ...


When the lux is greater than full scale, it just reverts to showing a reading of 1. So, you were on the second scale, which means the readings all need to be multiplied by 10. But, that says this T8 light gives more PAR than the Hagen Glo light. 

I notice that you can see two half images of a bulb on each side of both bulbs, so that is at least a fair reflector, while the Hagen Glo has a relatively poor reflector. Now I also wonder if the Hagen light also has an underpowered ballast. I think it is unlikely that your readings are wrong. But, readings with only one bulb will be very interesting too.


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## sowNreap (Jun 10, 2012)

Hoppy said:


> When the lux is greater than full scale, it just reverts to showing a reading of 1. So, you were on the second scale, which means the readings all need to be multiplied by 10. But, that says this T8 light gives more PAR than the Hagen Glo light.
> 
> I notice that you can see two half images of a bulb on each side of both bulbs, so that is at least a fair reflector, while the Hagen Glo has a relatively poor reflector. Now I also wonder if the Hagen light also has an underpowered ballast. I think it is unlikely that your readings are wrong. But, readings with only one bulb will be very interesting too.


I knew something was wrong when I converted the lux to par and it didn't seem right .. I had forgotten about the scale being 10x. 

Yes the reflector seems to decent. As the last photo shows on the right you can see 2 partial bulb images to the right of the bulb, then another image under the bulb and yet another to the left of the bulb. 

Got some more readings for you. I added readings taken at the very end of the fixture on the right side. In my 1st post where the chain attaches to the fixture, I called it "right end" now it's called "right/chain. And "right end" is the very end of the fixture. Sorry for any potential confusion. 

These were all done at night with the t8 fixture the only light on so these numbers may be more accurate but might be off from the previous readings. I got moving the fixture down pat so can breeze through fairly fast if you want readings taken in daylight again.

1st column is 2 bulbs lit. 2nd column is just 1 bulb lit .. front bulb. All readings used 2nd (10x) scale but in addition where I had to use 1st (1x) scale I gave that reading also. So in the column it will be 10x/1x. 

*15" height*
Center, Center of bulbs--------555 -----371
Center, 9" toward back--------345------256
Center, 9" toward front--------298------151
Center, 12" toward front-------228 -----117
Right/Chain, Center -----------426 ------278
Right/chain, 9" back-----------264 ------196
Right/chain, 9" front-----------219 ------116
Right/chain, 12" front---------173 ------090/905
Right very end, center --------265------176
Right very end, 9" back-------172-------125
Right very end, 9" front ------148 ------075/756
Right very end, 12" front------118------060/601

*20" height*
Center, Center of bulbs -------401------258
Center, 9" toward back -------308------220
Center, 9" toward front--------253-----125
Center, 12" toward front-------208-----101
Right/chain, center-------------302-----193
Right/chain, 9" back------------233-----172
Right/Chain, 9" front-----------186-----094/965 (probably leaned toward sensor too much when switching scale)
Right/chain, 12" front----------155-----078/783
Right very end, center---------205------130
Right very end, 9" back--------162------117
Right very end, 9" front--------139------069/683
Right very end, 12" front-------116------056/556

*22" Height* 
Center, Center of bulbs---------346-----220
Center, 9" toward back---------288-----202
Center, 9" toward front---------225-----113
Center, 12" toward front------- 191-----094/947
Right/chain, center--------------262-----165
Right/chain, 9" back------------ 218-----154
Right/Chain, 9" front------------171-----086/859
Right/chain, 12" front-----------141-----071/708
Right very end, center----------185-----117
Right very end, 9" back-------- 156-----111
Right very end, 9" front-------- 124-----063/635
Right very end, 12" front-------105-----053/530

*24" Height * (to compare since I did it before)
Center, Center of bulbs-------- 307-----195
Center, 9" toward back-------- 260-----186
Center, 9" toward front-------- 212-----106
Center, 12" toward front-------182-----087/873
Right/chain, center-------------230-----148
Right/chain, 9" back------------196-----145
Right/Chain, 9" front-----------160-----081/816
Right/chain, 12" front----------137-----068/680
Right very end, center---------169-----108
Right very end, 9" back--------144-----105
Right very end, 9" front------- 120-----060/607
Right very end, 12" front------104-----051/512

*25" height *
Center, Center of bulbs--------295-----176
Center, 9" toward back--------254-----177
Center, 9" toward front--------207-----104
Center, 12" toward front-------179-----086/859
Right/chain, center-------------224-----131
Right/chain, 9" back-----------195-----136
Right/Chain, 9" front-------- --156-----078/786
Right/chain, 12" front----------135-----065/653
Right very end, center---------164-----096/959
Right very end, 9" back--------143-----102
Right very end, 9" front------- 117-----058/587
Right very end, 12" front------102-----049/495

*30' Height*
Center, Center of bulbs--------224----- 144
Center, 9" toward back--------195------140
Center, 9" toward front------- 177------097/972
Center, 12" toward front------155------080/804
Right/chain, center------------173------111
Right/chain, 9" back-----------151------110
Right/Chain, 9" front----------138-------075/751
Right/chain, 12" front---------121-------062/625
Right very end, center--------136-------087/875
Right very end, 9" back-------118------ 086/859
Right very end, 9" front-------108------ 059/590
Right very end, 12" front-----095/952--049/494

I was going to do a 2nd set of readings but it got late ... might do it Saturday night if you think it would help. Otherwise I'll move on to the other fixture I bought (the 10-1/2 brooder clamp-on). I'm going to have that Lux meter wore out and out of calibration pretty quick. :red_mouth

Thanks for all your help, Hoppy ... I really appreciate it.

EDIT: wish now I'd added the previous readings into this new post to be able to compare them easier. Maybe I'll come back later and do that.


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## Wasserpest (Jun 12, 2003)

To get a general idea of how much a decent reflector improves the situation, could you black it out (black T-shirt or such) and do some basic measuring with one/two bulbs?

My gut feel is that a perfect reflector could roughly double the light intensity. Would be interesting to see some numbers though.


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## Hoppy (Dec 24, 2005)

Thank you sowNreap! This is all of the data I need for this light. Here is what it looks like charted on a PAR vs distance basis:









I would never have believed this! That light would need to be suspended about a foot above a 55 gallon tank to drop the intensity enough for a low light tank. Now it looks like the primary reason why T5 lights are so much better than T8 is the reflectors, much more than the brightness of the bulbs. So, a DIY T8 light, using good reflectors could be a very good, cheap way to light 120 gallon and bigger tanks.

The data for the clamp on dome reflector light will be very interesting too.


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## sowNreap (Jun 10, 2012)

Wasserpest said:


> To get a general idea of how much a decent reflector improves the situation, could you black it out (black T-shirt or such) and do some basic measuring with one/two bulbs?
> 
> My gut feel is that a perfect reflector could roughly double the light intensity. Would be interesting to see some numbers though.


I'll see what I can do late tonight. It would be interesting to see the results. 

And after I take down my aluminum foil lined 2xT12 shop light I might do readings for that just to see what effect the foil has. Then take the foil off and do another reading just too see how it compares. But those 2 may have to wait a bit. I'm going to get readings on the brooder light first since I wanted to use that on my 10 gal grow-out tank. And it may be more beneficial to everyone .. as long as Hoppy doesn't mind me imposing upon him to make more charts. :biggrin:



Hoppy said:


> {snipped ....}
> I would never have believed this! That light would need to be suspended about a foot above a 55 gallon tank to drop the intensity enough for a low light tank. Now it looks like the primary reason why T5 lights are so much better than T8 is the reflectors, much more than the brightness of the bulbs. So, a DIY T8 light, using good reflectors could be a very good, cheap way to light 120 gallon and bigger tanks.
> 
> The data for the clamp on dome reflector light will be very interesting too.


Thanks very much for the chart Hoppy!! I haven't had time to do the calculations. But my oh goodness .. I didn't think it would be THAT good! Thought I'd would need 2 of these fixtures for my tank but now looks like 1 is almost too much.

That almost complicates things more than I wanted. LOL I've got 2 sets of ceiling hooks for 2 light fixtures so they aren't centered over the tank. Now I'll have to figure out how to hang it or guess I'll just have to put more holes in the ceiling. 

If I gave you another reading for a single bulb could you chart that also? Does it hurt this type fixture to run them with just 1 bulb? I haven't looked at the numbers in detail and I assume one bulb probably won't give good coverage for a wider tank but just curious to see how it compares.

This forum has created a monster!!  I want to test everything now. Especially since that I have that great spot for hanging the fixture and have it all measured off and fixed up. And I hope it may help others.. sort of paying forward a bit for the help that everyone has given me.


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## Hoppy (Dec 24, 2005)

It is no imposition on me to do those charts. I enjoy doing that, so I do them for fun anyway. And the more different light fixtures we can get PAR data on the better it will be for everyone.

About the diamond plate light: are the reflectors aluminum, stainless steel, or what? You mentioned how light the fixture is, which makes me think they might be aluminum. And, did you ever figure out if they are plastic coated?

If you were to tape some sheets of black paper together to make a 4 foot long piece, then use that to block the light from hitting the reflector, PAR data from that would be a bare bulb with no reflector. That would tell us how much effect the reflector has.

I'm puzzled by the fact that the PAR for two bulbs is about 1.5-1.6 times the PAR for one bulb. I can't see why that would happen and why the ratio isn't 2 to one. Was the sensor centered under the one bulb or still centered under the middle of the light? Or was the sensor always under just one bulb? The latter might make the ratio 1.5 instead of 2.


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## sowNreap (Jun 10, 2012)

I'll check the fixture again and post back but think it's aluminum.I'll examine more thoroughly to see if it does have plastic coating. I didn't notice it or couldn't tell when doing the measurements. 

I don't have any black paper that I can think of. I do have a couple 2' long black towels I thought about trying to use. I'll have to scrounge around and see what I have available to "blackout" the reflector.

When I took readings it was always the center of the fixture even when I did single bulb. I moved the sensor forward debating whether I should do center of bulb and the lux went down, so that could be why that is off. Sorry. I already had the marks on the countertop for center of fixture so just went with that. I can measure off center of bulb and re-do if you want to get more accurate reading.


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## Hoppy (Dec 24, 2005)

If you just get 3 readings with the sensor centered under the "on" bulb that might tell us something. (I'm not sure what it will mean, yet.)

White thick paper would also work well to block off the reflector. That would simulate a normal T8 fixture with white painted background. The paper could just lay on the bulb.


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## sowNreap (Jun 10, 2012)

Would cardboard work? I have all kinds of boxes I could tear up. I thought about black trash bag but it seems too shiny. Oh .. thought of something. The black weed block cloth .. I'll have to see how transparent it is and how big the holes are. Might allow to much light through since designed to allow water to penetrate. 

Not sure I have any thick white paper, only printing paper but it appears to transparent. So no pure white or pure black that I've found yet ... but I'm still looking.

I'll take a few readings centered under single bulb. I assume you mean at different heights ??? Or 3 readings same height???


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## Wasserpest (Jun 12, 2003)

Cardboard would work great - pretty bad reflector.


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## sowNreap (Jun 10, 2012)

I actually found some black felt material. Held up to light, no penetration. Perfect. I knew if looked long enough I'd find the ideal thing. I come from a family that hardly ever throws anything away. LOL

Glad though that the cardboard would work. Just in case.


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## Hoppy (Dec 24, 2005)

Three readings at different distances, not all at the same distance. And, I only use the center reading, except for curiosity about how uniform the light is over the whole substrate.


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## Diana (Jan 14, 2010)

Lots of good work, here, sowNreap!

I see a couple of interesting things in some of these readings. 
When you were doing the 'one bulb' series, you said you were using the bulb at the front. 
Looking at the results, it looks pretty consistent that the readings taken at the back of the tank are almost always brighter than the readings taken at the equivalent location, but front. 
Theory: The closer you are to centered under the bulb the more restrike you are losing. Light that goes straight up from the bulb reflects straight back down and is re-absorbed into the bulb. When you are taking readings away from right under the bulb the reflection is more varied and you are seeing more of the reflected light because it is somehow reflected around the bulb. The diamond pattern is scattering the light. 

When you are too close to the surface (see first post with the charts, 10" test results) the maximum is a really large maximum right under the center of the fixture. Much higher light than all other locations. 
But when you raise the fixture the readings sort of even out. The middle-center is still higher, but not as extreme as the 10" above the counter test. The higher you go the more even the light intensity over the whole tank. 

Translating these ideas to an aquarium: The best reflector will not be a flat sheet, but should have some way of directing the light that starts off heading away from the tank so that light enters the tank. A parabolic reflector with some special 'bumps' directly over the bulb can do this. 
The higher you can place the fixture the more even the light will be. If you want a high intensity spot, then lower the fixture.


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## sowNreap (Jun 10, 2012)

Thanks Diana. I'm not real sure but think the wall is causing it to be brighter in back. ??? I now wish I'd hung that black cloth on the wall to see what effect that had on the readings. Maybe next time. I also noticed the higher the fixture the more even the light was. 

Hoppy, it does appear that what makes the fixture so shiny is a thin foil type coating. Maybe some type of a chrome plating process. ??? I was able to peel about a 4mmx8mm corner up. It stuck back down really good as I had a hard time peeling it back up again. But I'll probably glue it to keep it from tearing. Here's a photo showing that. Used super macro about 2" away and then cropped heavily. 










The plastic I first noticed is clear like what the fixture was packaged in and is stuck to the rivets and screws. Here's a pic of that. Again super macro about 1" away and cropped. The rounded black thing is a reflection of the camera lens to give some perspective. 











Here's a photo of the fixture with the black felt type cloth I used to block the reflector:










Hoppy I didn't see your reply so I took most of the same readings as before. I eliminated the reading taken where the chain hangs and just did the very end. Since I took them, I'm including them here. Keep in mind this is not scientific quality measurements I'm doing the best I can with what I have to work with so I could be off as much as 1/8". I need a better more accurate way of measuring. 

1st column is blacked out reflector with 2 bulbs lit. The 2nd column is not blacked out but with only 1 bulb lit reading from the center of front BULB not center of fixture. As before, all readings used 10x scale but in addition where I had to use 1x I gave that reading also. So in the column it will be 10x/1x

*15 Height* ...............................................*Blacked Out* ... *1 bulb* ....... *middle between both bulbs to show difference*
Center of fixture, Center of single BULB -------- 213--------------282--------323
Center of fixture, 9" back -------------------------176-------------259
Center of fixture, 9" front ------------------------146--------------133
Center of fixture, 12" front -----------------------113---------------114
End of fixture, Center of BULB -------------------092/919----------119--------139
End of fixture, 9" back----------------------------078/786----------124
End of fixture, 9" front----------------------------068/685--------063/629
End of fixture, 12" front--------------------------057/575--------054/542

*20" Height*
Center of fixture, Center of single BULB --------150-------------227---------239
Center of fixture, 9" back------------------------134-------------204
Center of fixture, 9" front------------------------118-------------115
Center of fixture, 12" front----------------------100-------------091/909
End of fixture, Center of BULB------------------073/734--------111----------119
End of fixture, 9" back----------------------------066/664-------106
End of fixture, 9" front---------------------------060/601--------061/608
End of fixture, 12" front--------------------------054/541--------049/489

*25" height*
Center of fixture, Center of single BULB ------113---------------168----------174
Center of fixture, 9" back-----------------------105---------------161
Center of fixture, 9" front-----------------------095/954---------104
Center of fixture, 12" front---------------------085/849---------079/789
End of fixture, Center of BULB-----------------062/617---------090/899------094/942
End of fixture, 9" back--------------------------057/570---------089/891
End of fixture, 9" front--------------------------052/526----------055/555
End of fixture, 12" front-------------------------048/485----------044/445

*30" height*
Center of fixture, Center of single BULB-------088/881----------130----------134
Center of fixture, 9" back-----------------------085/849----------130
Center of fixture, 9" front-----------------------077/775----------091/910
Center of fixture, 12" front---------------------071/709-----------070/700
End of fixture, Center of BULB-----------------051/515-----------077/774-----078/782
End of fixture, 9" back--------------------------049/490-----------077/775
End of fixture, 9" front--------------------------046/460------------052/524
End of fixture, 12" front-------------------------043/430-----------042/420

Sorry the columns are off a bit. Can't get them lined up all nice & purdy. LOL

What I find interesting is how close some of the readings are for the blacked out 2 bulbs VS non blacked out single bulb.


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## Hoppy (Dec 24, 2005)

I charted these data points, center of the tank only, using the blacked out 2 bulb, and the one bulb with reflector readings:









I interpret this to show that a good \_/ shaped reflector increases the PAR from the bulbs by little more than 100% - it roughly doubles it. This is what I found with a similar shaped DIY reflector and a horizontal screw-in CFL bulb. But, this also suggests that even T8 lights can have substandard ballasts. The T8 aquarium light I tested, which had white plastic flat surfaces behind the bulb, no real reflector, gave significantly less PAR than this one does. I know that light was fairly old, but I thought it did have an electronic ballast. The light was sometimes reluctant to light up, so it might have had a simple inductor ballast. If it didn't have an electronic ballast, this difference may be the effect of using an electronic ballast in the diamond plate light.


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## Wasserpest (Jun 12, 2003)

Thanks a lot sNr for the measurements, and Hoppy for the graphing expertise. Confirms what I suspected. Using good reflectors is a huge factor!


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## sowNreap (Jun 10, 2012)

Thanks Hoppy for the new chart. It's really an eye-opener and very helpful. I know you only use the center for these charts but now realize how much lower the light at the ends are so I can make sure to plant any higher light plants more toward center (which I usually try to do but measuring the end really shows it).

Now I'll need to figure out how best to utilize it to achieve high-low light or low-medium light without having the plants grow toward the light if using 1 bulb. For right now think I'll just hang it higher until I figure out how I want to do it since I have several options. Now I can get rid of the 3x40watt bulbs and use 1 or 2 - 32 watt and cut electricity usage a little bit .. hey every little bit helps. 

The fixture I'll be replacing is a very old T12 white painted plant grow light. I'm going to test it to see how it compares with Hoppy's old T8. I don't know what kind of ballast is in it.

Now on to testing the 10-1/2 clamp-on light.

EDIT: Thanks Hoppy .. I see you added the chart to the Par vs distance thread. That might help people find it easier.


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## MichaelMcG (Mar 16, 2012)

wow thanks alot guys! this thread answered so many questions for me about these lights.


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## driftwoodhunter (Jul 1, 2011)

I'm so glad I saw a post that linked to this - I missed it somehow. 

I've been using this HD diamond plate fixture for a year or so, first on a 55, now on my 125. I am considering a second one for the 125 due to the front-to-back depth of the tank, and for short light bursts. I LOVE these fixtures, and I run a low light/low tech tank yet I still get some algae in the tank (my light rests directly on the tank's Versa Glass lids, and I use no Co2) I have always thought the "W" shaped mirror finished reflector was good enough for my needs. If I could keep the light from shining in my eyes, I'd raise it a bit and go with just the one light.

Thanks for all the time consuming work that went into this!


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## sowNreap (Jun 10, 2012)

driftwoodhunter said:


> I'm so glad I saw a post that linked to this - I missed it somehow.
> 
> I've been using this HD diamond plate fixture for a year or so, first on a 55, now on my 125. I am considering a second one for the 125 due to the front-to-back depth of the tank, and for short light bursts. I LOVE these fixtures, and I run a low light/low tech tank yet I still get some algae in the tank (my light rests directly on the tank's Versa Glass lids, and I use no Co2) I have always thought the "W" shaped mirror finished reflector was good enough for my needs. If I could keep the light from shining in my eyes, I'd raise it a bit and go with just the one light.
> 
> Thanks for all the time consuming work that went into this!


So how has your fixture held up over the past year? Reviews on Home Depot aren't real good so great to know you've been running one for so long for aquarium use.

Any trouble with the chrome plating peeling or coming off? Any problems with ballast? Or maybe I should just ask if you've had any problems at all with the fixture. LOL 

I know you said you've got glass between the fixture & water, but have you had to clean the fixture at all? 

I got mine temporarily hung up and yeah that sucker is really bright in my eyes! Especially compared to the 2 units I took down. Right now I have the cord weighing down the front of the fixture to tip it down a bit to keep the blinding light out of my eyes. LOL I can see I'm not going to be able to hang it high unless I rig up some type of shield.


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## driftwoodhunter (Jul 1, 2011)

Yes, it is bright and hard on the eyes - I'll have to design some kind of shield too. I was thinking of a faux canopy - just the four sides and an open top & bottom. That way it could be tall enough to block the light from my eyes when I'm sitting down, yet leave easy access to lift the Versa tops to feed the fish. Maybe if the faux canopy is tall enough (say 10"?) I could suspend the light from it rather than the ceiling, and hinge a panel on the front to access the Versa tops instead of from the top opening. It doesn't make sense in type, but the imaginary picture in my head does - lol. If I build one I'll post it in a tank journal I want to start.

I started using my light in September of 2011 - you can see it in the first pic of my 29 tank's journal in my signature. I've had no trouble whatsoever out of it. It's still clean as a whistle underneath. Lights perfectly every time. I've even dropped a few times when taking it off the tank to do tank work - I'm a clumsy gal - and no problems. I did buy the clear plastic tube shields for the bulbs when I bought the fixture and the lights to protect the bulbs from water splashes. HD has them for sale next to the light fixtures for less than $1 a piece. The plating looks as pristine as it did when I bought the light - I didn't even realize it was plated until I saw this thread! LOL The light has been in constant daily use since I bought it. It's what I'll be buying for my 55 and maybe my 40B (I use natural light from a nearby window on it now). I'm also an artist and I like the quality of light so well I'm switching out all my overhead studio lights for this one.


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## sowNreap (Jun 10, 2012)

Thanks Driftwoodhunter for that great news about this fixture!! I really like it. I guess I like shiny things. LOL

I'll have to look again at those bulb protectors I think they were almost $4/each at my store. One thought I had was wrapping them with fiberglass insect screen and then put them over the bulbs to filter the light. Might be the easiest way to "attach" it to the fixture. I'll probably try this first & then take some readings to see how much it cuts down the light. 

I don't have any tops for my tank. The fish sometimes splash a bit when in spawning mode. Mostly when the male chases the females all over the tank. So far none have ever come close to escaping. 

That's a nice looking tank but the post says it's a 55 gal and had me confused for second.  And to get a bit off topic since you mentioned shiny fish in the thread, I have another tank with a mix of long finned and regular black skirted tetras. I like the way they flash & shimmer in the light. Have an iridescent look to them which is pretty cool.


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## driftwoodhunter (Jul 1, 2011)

Thanks, sowNreap : )

My best friends who are husband & wife, also love shiny things. We call ourselves the Three Old Crows - lol

The links under my signature are to a 55g tank that has since been torn down, and two 29g tanks that are still up. I haven't made a journal for the 125 yet. The HD fixture had been on the 55 but it's on the 125 now so I'll have to buy another light when I set the 55 back up.

Here are some pics of the 125g with the HD diamond plate light resting on top... mind you, this is a deep tank, and you can see light gets to the bottom (better than I expected it to)

the left side









the middle









the right side









you can see the back of the tank is still dark - I have the light sitting as close to the front edge as possible. During the day the back side of the tank gets ambient light from kitchen windows. When I get home from work and turn the shop light on, I position it to the front as in these pics, or the back to create a dramatic back light look I like. The fish seem to enjoy having dark areas to go to and I like the more tranquil effect of not having everything lit all the time. You can easily see how the 4 foot light doesn't reach well into the sides of a six foot tank. That changes when I hold the light up a few inches. One reason I'd like to create a shield and raise the light. Having said that, I have plants that like lower light at the edges now and it works just fine.


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## sowNreap (Jun 10, 2012)

Wow .. another nice looking tank! My fish would probably like having some darker areas. They get a bit skittish with this bright light.

I see now that my other computer (the monitor just died on it so using a spare) cut off the bottom of your post so I didn't see the 2nd link to the 29 gal no wonder I was confused. LOL It shows up fine on my laptop.


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## sowNreap (Jun 10, 2012)

I bought a couple plastic bulb protectors at HD. I then cut 1.75” strips of window screen to fit half way around inside the plastic tube to dim the light and lower fixture down. Here's the Lux readings for that. 

I took these readings all using 2 bulbs lit (same order as columns below): 2 bulbs no blocking of light, plastic tube protector, ½ diameter window screen inside tube. I did the 2 non-blocked bulbs again just to see if my numbers are consistent with previous readings. 

I put the center ones first to make it easier for you Hoppy. And I know you don't need the readings other than center, but I took them for myself so figured I'd post them anyway. 

I didn't allow sensor thickness for these. 
*Center of fixture, Center between bulbs*
Height ----- No block –---- Plastic tube ------- ½ screen
15” ----------- 557 -------------- 506 -------------- 346 
20” ----------- 388 -------------- 362 -------------- 239 
25” ----------- 290 ---------------268 -------------- 177 
30” ----------- 221 -------------- 205 -------------- 135

Adjusted for sensor thickness which I think is about 26mm .. I just used 1”. 
*Center of fixture, Center between bulbs*
Height ----- No block –---- Plastic tube ------- ½ screen
15” ----------- 505 -------------- 476 -------------- 313 
20” ----------- 360 -------------- 327 -------------- 222 
25” ----------- 268 ---------------244 -------------- 163 
30” ----------- 205 -------------- 189 -------------- 128 


All locations, I didn't allow for sensor thickness
*15” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center --------557 -------------- 506 -------------- 346 
Center, 9” front ------ 282 -------------- 276 -------------- 172 
Center, 12” front ----- 211 ---------------206 --------------124 
Right, Center --------- 247 -------------- 221 -------------- 155 

*20” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center ------- 388 -------------- 362 -------------- 239 
Center, 9” front ------ 233 -------------- 236 -------------- 148 
Center, 12” front -----188 ---------------194 -------------- 118 
Right, Center --------- 197 -------------- 180 -------------- 117 

*25” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center ------- 290 -------------- 268 -------------- 177 
Center, 9” front ------ 198 -------------- 184 -------------- 121 
Center, 12” front -----165 ---------------162 -------------- 103 
Right, Center --------- 160 -------------- 146 -------------- 991=1x 

*30” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center ------- 221--------------- 205 -------------- 135 
Center, 9” front ------ 166 -------------- 161 -------------- 102 
Center, 12” front ------142 --------------142 -------------- 903=1x 
Right, Center --------- 130 -------------- 120 -------------- 801=1x 


I adjusted for sensor thickness which is approx 26mm .. I just used 1”.
*15” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center ------- 505--------------- 476-------------- 313 
Center, 9” front ------ 275 -------------- 273 --------------165 
Center, 12” front -----213 ---------------206 -------------- 122 
Right, Center --------- 240 -------------- 212 -------------- 157 (left end, center - wasn't as accurate quit using) 

*20” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center ------- 360--------------- 327 -------------- 222 
Center, 9” front ------ 225 -------------- 215 -------------- 144 
Center, 12” front -----186 ---------------187 -------------- 118 
Right, Center --------- 180 -------------- 164 -------------- 126 (left end, center - wasn't as accurate quit using)

*25” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center ------- 268 -------------- 244 -------------- 163 
Center, 9” front ------ 179 -------------- 179 -------------- 125 
Center, 12” front -----161 ---------------153 -------------- 105 
Right, Center --------- 146 -------------- 133 -------------- 884=1x 

*30” Height*
Location ----------- No block –---- Plastic tube -------- ½ screen
Center, Center ------- 205 -------------- 189 -------------- 128 
Center, 9” front ------ 156 -------------- 153 -------------- 101 
Center, 12” front -----137 ---------------134 -------------- 876=1x 
Right, Center --------- 122 -------------- 110 -------------- 750=1x 


I'm not sure what I want to do. I'm close to where I think I need to be light intensity wise for high-low or low-medium light. I'm about 22"-23" from substrate but that may change soon. If I lower the fixture there's not enough light spread. The window screen inside the tube at the height needed for spread cuts the light intensity too much. But it did help some with the spillover light. I could gain about 6-7% if I didn't use the plastic tube (if I calculated right). Another option is to get a 2nd fixture and use 1 bulb from each then lower it to 20” and use the ½ diameter window screen to block light. It's either that or raise the fixture higher and figure out a way the block the spillover light. I may try that first since I'm to cheap to buy another fixture. LOL Or I may take readings on my aluminum foil lined T12x2 to see what lux readings it gives me & use it in addition to the Diamond Plate fixture.


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## driftwoodhunter (Jul 1, 2011)

I'm so surprised the plastic tube made a noticeable difference!

I don't want to suspend the light from my ceiling, but I have seen builds here that use bent conduit tubing to hang the light from (the conduit being attached to the wood tank stand by "U" shaped brackets). That is something I'd try - but I still have to come up with an appealing way to block the spillover light - it's just too hard on the eyes. I've been too busy at work to dwell on it, but it's still a project in my head. If you find a solution, please post it here! I can do basic woodworking, and I do stained glass work, so I am thinking about making a kind of cover that mimics the rectangular stained glass bar or kitchen island lights...probably more trouble than it's worth - lol.


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## Hoppy (Dec 24, 2005)

I updated the chart for T8 bulbs here: http://www.plantedtank.net/forums/showthread.php?t=184368 I suspect if the window screen wrapped all the way around each bulb it would have dropped the PAR by closer to 40% instead of 30% (plus 8% drop due to the plastic sleeves.) So, the protective sleeves, with a complete cylinder of window screen should drop the PAR by almost half.

If you want to end up with about 35-40 micromols of PAR at the substrate, remember, you will get at least 10% more than the chart shows - more than your data indicates - due to the slight focusing effect of the air to water interface. So, you would want to pick a height that gives you about 30-35 micromols, as shown on the chart, not 35-40. If you plan to add a layer of window screen and the protective sleeves, that number would be about 60-70 micromols, to allow for the effect of the screen and sleeve. So, the height should be 18-20 inches.


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## driftwoodhunter (Jul 1, 2011)

I am so pleased - it seems that the HD diamond plate fixture provides par readings right in the ballpark for what I want in my 125, based on Hoppy's earlier recommendations when I asked for his help determining how much par I needed to create the kind of tank I wanted. If I raise the light, I will remove the plastic shields.

Plants that do well with less light are at the edges of the tank. As a matter of fact, I was starting to have algae issues with some anubias hastifolia that was in the center of the tank, a few inches above the substrate in a rock grouping. I moved them closer to the edges of the tank and down lower, and the algae quickly cleared up and the plants went from a sickly lemon/lime color to a fine green. Plant growth is slow (I find it wonderfully slow - that's a huge part of the planted tank appeal for me) but the growth is healthy. The fish like the darker regions of the tank, and I love the moody atmosphere of the low light and darker pockets. It was just dumb luck and being broke that had me looking for inexpensive light and led me to try the diamond plate fixture. So thrilled to see all the work you folks have done, it really helps me to understand the delicate balance of light, CO2, etc. Thank you for all your effort!


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## sowNreap (Jun 10, 2012)

@Driftwoodhunter, I really like the idea of stained glass. That would be pretty cool looking! If I come up with any ideas I'll post them here. It surprised me that this light does as good as it does. I considered getting a custom or even regular Catalina fixture but got sticker shock when I called about pricing. I figured I'd try the cheaper fixture first & if it didn't work out could always take it back and order the Catalina or try something else. Having that $13 Lux meter is proving to be money well spent!

@Hoppy, Thanks for the new chart. I hope my readings were consistent with my previous ones. I cut a piece to wrap all the way around inside the tube but it looked really dark in the tank so I didn't test that. I also didn't test to see how much, if any, effect rotating the screen to the upper half of the light would have. Visually it does appear to make a difference. At least to my eye it seems to make the tank a little bit lighter, but the light spillover is then too much. Sometimes I'll rotate the screen to the side which blocks some spillover but seems to give the tank a bit more light. That's the cool thing about using inside the tube .. it can be rotated as needed. LOL I may test those different positions just to see if there is a difference and just because I can. 

Also, I forgot about the additional 10% so I may be pretty good where I'm at. I'll have to re-calculate. The spillover isn't too bad at the height I have it now with the screen. Plus when my Bluegill gets done spawning I'm going to redo the substrate and remove a fake log I have and put in some driftwood. At that time I'll make sure to place my higher light plants more to the center (I tried to do that anyway but the Bluegill picked the center to spawn and now the plants have been moved to an end). 

It's too bad someone doesn't sell this fixture with just 1 bulb at half the price of course. Then buy 2 fixtures to get good spread .. that would be ideal.


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## Hoppy (Dec 24, 2005)

I made a mistake in the conversion factor going from lux to PAR units, for the Mastech lux meter. It is 76 lux per PAR unit, not 61. I corrected the chart of PAR vs distance.










I left the line for bulbs with protective sleeves off the chart, intentionally.


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## sowNreap (Jun 10, 2012)

Ok. Thanks for the update. I'll use the new conversion number for any future tests.


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## canlax (Sep 8, 2012)

Thanks for starting this thread!

I am working on my 210 gallon (84x24x24) and decided to go with 2 of these fixtures to start. They will be about 1.5 inches above the surface of the water. Since they are 4ft in length I have them staggered with the overlap happening in the middle over top the glass bracing. 

Do you think the fixture at 23" above substrate will have enough spread to go from front of tank to back of tank? I haven't put bulbs in the fixture yet as I am taking my time with the canopy that will house the lights.


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## Hoppy (Dec 24, 2005)

This gives the answer.


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## sowNreap (Jun 10, 2012)

And to makes things even easier especially since I may need to adjust my lights now .. and for those that may not realize that you need to add a ZERO to end of the Lux numbers and then divide by 76 here's the converted "PAR" numbers. It's so much easier to just look at the PAR numbers rather than having to keep converting them. LOL I usually use the charts unless I want to know how much spread I'll get at a particular height.

22' height taken at night only 1 reading
Center, center of bulbs -----------------------345 = 45.4 PAR
Center, 9" toward back -----------------------273 = 35.9 PAR
Center, 9" toward front -----------------------233 = 30.7 PAR
Center, 12" toward front ---------------------196 = 25.8 PAR
Right end, center of bulbs --------------------257 = 33.8 PAR
Right end, 9" toward back --------------------209 = 27.5 PAR
Right end, 9" toward front ------------------- 177 = 23.3 PAR
Right end, 12" toward front ------------------147 = 19.3 PAR

24" height (not sure why I did 24" meant to do 25" .. oh well, next time)
Center, center of bulbs -------293 = 38.6 PAR----298=39.2 PAR
Center, 9" toward back -------259 = 34.1 PAR----247=32.5 PAR
Center, 9" toward front -------204 = 26.8 PAR----209=27.5 PAR
Center, 12" toward front ------173 = 22.8 PAR--- 175=23.0 PAR
Right end, center of bulbs ---- 223 = 29.3 PAR--- 219=28.8 PAR
Right end, 9" toward back ----196 = 25.8 PAR----183=24.1 PAR
Right end, 9" toward front ----159 = 20.9 PAR----157=20.7 PAR
Right end, 12" toward front ---130 = 17.1 PAR----134 = 17.6 PAR

25" height
Center, Center of bulbs--------295 = 38.8 PAR
Center, 9" toward back--------254 = 33.4 PAR
Center, 9" toward front--------207 = 27.2 PAR
Center, 12" toward front-------179 = 23.6 PAR
Right very end, center---------164 = 21.6 PAR
Right very end, 9" back--------143 = 18.8 PAR
Right very end, 9" front------- 117 = 15.4 PAR
Right very end, 12" front------102 = 13.4 PAR

Ummm ... now I can better visualize how much my readings are off due to small inaccuracies in measurements.

And dang ... forgot I still need to add 10% to all these numbers to allow for the focusing effect of the air to water. I'm close to where I want to be .. maybe just make a couple minor adjustments. Or maybe I'll leave it and see how the plants grow.


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