# help with light kelvin



## Doomer (Jan 5, 2003)

If you want a heavily planted tank you need to shoot for 5500k to 6700k. Mixing bulbs with different ratings will not get you where you want to be. Go with PC retrofit kits from AH Supply. If you try this on the cheap with Home Depot lighting you will most likely fail or at best be severely limited as to the types of plants you'll be successful with.


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## 2la (Aug 18, 2002)

Doomer said:


> If you want a heavily planted tank you need to shoot for 5500k to 6700k.


Sorry, but this has to be one of my all-time pet peeves. There is nothing that says plants "need" bulbs of color temperature in this range--they could care less! Kelvin only tells you what kind of hue the bulb puts out (i.e., as perceived by _your_ eyes); it says nothing about spectrum (see here and note how different the spectra of all the 5000K bulbs are, or of all the 6500K bulbs are), and all else being equal the spectrum can make the difference in the type of growth you achieve. My friend uses all 5000K or 6000K bulbs; his plant growth is vigorous but leggy, with long internodes between the leaves. I use predominantly 9325K bulbs that feature a heavy spike in the blue spectrum on all of my planted tanks; my plant growth is somewhat slower, but bushier...


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## chinaboy1021 (May 30, 2003)

sweet tank!!!! whats the dimentions thanks!


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## 2la (Aug 18, 2002)

Thanks, it's 36"L x 17"H x 15"D, 40-gallon breeder.


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## aquaverde (Apr 15, 2003)

You've done a great job with that. The tank looks bigger than it is in that photo. The tank has incredible depth for the 15" dimension. Also, that's the first planted tank of that size I've seen. It's just not one of the stock sizes you might find anywhere. How much light do you have over it?

James


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## GulfCoastAquarian (Jul 30, 2002)

2la said:


> Doomer said:
> 
> 
> > If you want a heavily planted tank you need to shoot for 5500k to 6700k.
> ...


I agree. Far too often, I see people regurgitating the 5500K-6700K recommendation for planted tanks. While this guideline is mediocre at best for a beginner to get started, a serious planted tank enthusiast should try and optimize their lighting by researching and experimenting with the needs of their plants.
That being said, those 9325K bulbs seem to have one of the most closely matched output spectrums to that of a typical aquatic plants Photosynthetic Action Spectrum. I'm thinking about getting a set when I replace the marine 5500K bulbs I have now.


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## Doomer (Jan 5, 2003)

Funny, when I was starting out and asking questions anyone who dared to suggest anything other than 5500k to 6700k was ridiculed. 

Now, today, I make what I was led to believe, was the correct suggestion and now I'm wrong.


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## Wasserpest (Jun 12, 2003)

Could someone suggest a source for reasonably priced *T8*'s with a good spectrum and color temperature for planted tanks?

I am using super-cheap 5000K bulbs now, but I would like to try something "whiter" and more suited to create the bushy plant growth 2la enjoys.


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## GulfCoastAquarian (Jul 30, 2002)

Doomer, you're not wrong. And the 5500K to 6700K guideline is still somewhat valid, but it isn't completely accurate. There are tons of 5500K bulbs that aren't nearly as suitable for growing aquatic plants as plants with Kelvin ratings much higher than 6700K. But that's the fun part of this hobby - learning and understanding more so that you can continually improve the environment your plants grow in. 

It's obvious that chinaboy1021 is just starting out so your advice was definitely helpful in that it sent him in the right direction. 2la's advice simply takes it a step further. 

Also, to answer a question that chinaboy1021 initially posted - combining the light from a 5000K bulb and a 10,000K bulb does not create the equivalent of a 7,500K bulb. This is part of the reason why "Kelvin rating" is actually a poor way to choose plant growth bulbs. But if you're simply looking for a way to start out - look for daylight type bulbs in the range Doomer suggested and you'll be off to a decent start.


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## 2la (Aug 18, 2002)

Doomer said:


> Funny, when I was starting out and asking questions anyone who dared to suggest anything other than 5500k to 6700k was ridiculed.
> 
> Now, today, I make what I was led to believe, was the correct suggestion and now I'm wrong.


Doomer, I sincerely apologize for the harshness of the tone of my post--sometimes the proper tonality doesn't transmit well through the written word. I meant only to soften the absoluteness of the word "need," not to challenge the concept as a good guiding principle. While there's always a danger in taking the exception for the rule, it's unfortunate that those who are already experienced in a certain field are sometimes so quick to disregard or, as you wrote, even ridicule those who try to offer alternative points of view that they may perceive to challenge or threatened established 'norms'. When that happens, the opportunity to augment--not necessarily _replace_--the existing body of knowledge is drowned out by the flood of criticism that often comes in return. The notion of plants "needing" a certain color temperature is one I've tried to address each chance I get; another is that DIY CO2 is absolutely not feasible in tanks over 30 or 40 gallons (a local aquarist who grows THE healthiest, most robust plants I've ever seen--commercial or private--uses DIY CO2 on a 75G tank, though it takes a fair amount of upkeep).

Apologies,

2la


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## 2la (Aug 18, 2002)

aquaverde said:


> You've done a great job with that. The tank looks bigger than it is in that photo. The tank has incredible depth for the 15" dimension. Also, that's the first planted tank of that size I've seen. It's just not one of the stock sizes you might find anywhere. How much light do you have over it?


Wow, James, thanks--that's both incredibly flattering and rewarding to read! I always wonder how my own tastes and capabilities stack up to those of other aquarists, so it's nice to get such positive input from a respected fellow aquatic gardener.

I honestly can't recall if this is an All-Glass, Oceanic, or Island tank, or some other brand. I got this tank a few years ago at cost from a local wholesaler when I worked for a scientific supply company and purchased the tank under the premise that I was a purchasing for a local grade school that was conducting experiments on aquatic plants. I know, I know, not the most scrupulous of means, but I'd been screwed over by my company so many times I figured I might as well get _some_ kind of baby out of it... :wink: :twisted: The standard 40-gallon breeder from All-Glass has similar dimensions, but the height and depth are reversed--much nicer for front-to-back depth in a planted tank! As it is, I have to try a little harder to create the illusion of depth.

As for lighting, I have four 30-watt fluorescents over it, arranged thusly from back to front:

GE Aqua Rays Fresh & Saltwater (9325K)
Coralife Trichromatic (6500K)
GE Aqua Rays Fresh & Saltwater
GE Aqua Rays Fresh & Saltwater

I include the Trichromatic only to enhance the greens, and it works well in the position above because it's situated over the green Myriophyllum matogrossense. I've also used Coralife Day Max, Penn Plax Ultra TriLux, and GE Chroma 50 tubes in this position to similar effect.


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## m.lemay (Jul 28, 2002)

> That being said, those 9325K bulbs seem to have one of the most closely matched output spectrums to that of a typical aquatic plants Photosynthetic Action Spectrum. I'm thinking about getting a set when I replace the marine 5500K bulbs I have now.


Sam: check out my post in the lighting section entitled "Verdict on 55 watt PCs", for some input on those 9325ks. So far, they're the best thing I've found. I wish someone sold them a little cheaper though. But they are worth it.

Marcel


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## chinaboy1021 (May 30, 2003)

thanks a lot guys! it's starting to come together now!. 

btw, i hate guidelines too. such as 1 inch per gallon. blah blah blah bs. but it's a place to start.


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## aquaphish (Dec 20, 2002)

Is Kelvin rating something to do with the amount of light from the bulb and the true sunlight? I thought I read that @ 5500K a light would represent the sunlight at noon, at a certain depth of water. And the higher the K the deeper the depth of water. 

I a most likely wrong but I thought I read something to this effect.


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## 2la (Aug 18, 2002)

A link discussing the differences between the color temperature of the sun versus the color temperature of fluorescent lights (and why attempting to match them is overrated in terms of plant growth).

A link discussing color temperature, PAR, and PAS. They're a bit science-heavy, but hopefully you can get something useful out of it!

2la


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## GulfCoastAquarian (Jul 30, 2002)

The color temperature doesn't have anything to do with true sunlight per se, but it just so happens that bulbs with a color temperature around 5500K most closely resemble sunlight at noon at the surface of the water (or less than two feet deep). Deeper water depths absorb the red and green spectrums and leave mostly blue, so yes, a higher color temperature might indicate deep water bulbs. But not always. The 9325K GE Aqua Rays bulb is no where near as blue as a 7100K Actinic bulb. 
Just goes to show you - color temperature can be a decent "guide" but I wouldn't make my final selection based on it alone.


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## m.lemay (Jul 28, 2002)

Kelvin rating refers to when a piece of carbon is heated to a certain temperatur it'll glow a certain color. For instance,when carbon is heated to 3000 degrees kelvin it'll glow reddish. When that same piece of carbon is heated to 15,000 degrees kelvin it'll glow bluish and so on. What does this all mean for your planted tank,... not a damn thing. This measure really only tells you what the light looks like to the human eye. 

What really matters is PAR (photosynthetic activity rating)which really has a lot to do with the spectrum distribution of the light. Plants do not react to green light to photosynthesize. The like the red and the blue spectrums. Unfortunately there isn't much data out there on PAR ratings for flourescents but there is some. Check out the post at the top of the lighting section:


http://www.plantedtank.net/forum/viewtopic.php?t=819


Marcel


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## 2la (Aug 18, 2002)

Actually, Marcel, there is no such thing as "photosynthetic activity rating." PAR stands for photosynthetically active radiation, and is often used more loosely than it should or in an ambiguous way. It's essentially just a fancy schmancy term for visible light!  See the link I cited in my previous post for an explanation of the difference between PAR and PAS, but by all means correct me if I've misunderstood anything...


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## m.lemay (Jul 28, 2002)

I still stand by the fact that Kelvin ratings mean nothing for plant growth. I think everybody else got the idea. I've also seen it referred to as PUR as in the link I referred to. The point was plants prefer the blue and red ends of the spectrum regardleess of color temp ratings.

Marcel


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## m.lemay (Jul 28, 2002)

http://www.plantedtank.net/forum/viewtopic.php?t=819. Heres another link.


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## 2la (Aug 18, 2002)

No, I agree completely about Kelvin ratings (I was the one who brought it up in this thread, after all)...I was just pointing out a technicality--didn't mean to offend, just trying to educate...


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## m.lemay (Jul 28, 2002)

No offense taken. 8)


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## aquaverde (Apr 15, 2003)

I'm not up on this subject technically, although I understand the concepts. I have two identical fixtures for my 20xh, both have the same polished German reflectors. One has 36W PC 6700K bulb, the other has a pair of 15W NO flouros: one non-descript Catalina Aquarium purplish-hued grow bulb and one GE P&A bulb. Can't quote lumens for any of it, but the 36W PC has to be twice as bright as the 30W NO. I had the NO over the tank before I got the PC bulb, then switched to the PC. Due to a bumper crop of algae (BBA 1/4" thick engulfing some plants, green spot, hair, fuzz, etc.) I decided to go back to the NO since it seemed the algae was the only thing benefitting from the slight boost in wattage. Now get this. The tank is now very dim to the eye, but the sunset hygro got pink in one day after the change(no pink under the 6700K). 

It remains to be seen if this inhibits the algae, but as far as I'm concerned, lumens are about a useless parameter from the standpoint of a planted tank. If I had the flexibility in this tank, I would try what 2la did with adding one lamp for appearance' sake, but that's not an option.

How's that for a roundabout way to agree with Marcel :wink: 

James


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