# Is 1850 Lumens "Bright"?



## Argus (May 22, 2013)

I've ordered a SeaClear 30g tank that is 36" x 12" x 16"high. I have the 36-48" Fluval Aquasky LED Aquarium Light that claims to put out 1850 lumens. 

In choosing plants, I need to know if this is considered bright, moderate, or low light?


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## mattinmd (Aug 16, 2014)

I'll be blunt... Lumens isn't a very useful number here, but it is one that is easy for MFG's to specify, because it's how room lighting is specified.

Lumens measures total light produced (including light not shining into your tank) and is spectrum weighted to human eye response (which is strongly green dominant).

Plant growth is going to depend on the intensity of light shining on them, and is going to be spectrum weighted to photosynthesis (which is slightly more responsive to red/blue than green).

So you really have to be careful when trying to use lumens as a plant-growth basis.. You can have high lumen fixtures with relatively little benefit to plants, and you can have lights that benefit plants a lot with very low lumens.


I don't think anyone has made any PAR measurements on this light, but there's some speculation out there that it is similar to the Sat+:

http://www.plantedtank.net/forums/showthread.php?t=875473

That honestly seems like a fair comparison, the Aquasky has only slightly higher wattage and lumens than the Sat+, but the same beam angle... 

36" sat+ - 1500 lumen, 25 watt, 120 degree, 28 PAR at 18"
36" aquasky - 1850 lumen, 27 watt, 120 degree, ?? PAR

Regardless, at 16", with slightly higher output than a Sat+, you're probably looking at the lower end of medium light or upper limits of low. 35-ish PAR? (all of this assumes you run the light at max brightness)

Sources:
http://current-usa.com/aquarium-led-lights/satellite-led-fixtures/satellite-freshwater-led-plus/

http://fluvalaquatics.com/us/freshwater/aquarium-lighting/series/aquasky/


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## Argus (May 22, 2013)

mattinmd said:


> I'll be blunt... Lumens isn't a very useful number here, but it is one that is easy for MFG's to specify, because it's how room lighting is specified.
> 
> Lumens measures total light produced (including light not shining into your tank) and is spectrum weighted to human eye response (which is strongly green dominant).
> 
> Plant growth is going to depend on the intensity of light shining on them, and is going to be spectrum weighted to photosynthesis (which is slightly more responsive to red/blue than green).


Just for laughs I measured the light's "white" setting with a photographic color temp. meter. It was about 7200K where daylight is generally considered to be about 5600K. So, strongly toward blue. This measurement is too simplistic to know whether it is biased toward red & blue vs. green, but the general balance is toward blue.




> So you really have to be careful when trying to use lumens as a plant-growth basis.. You can have high lumen fixtures with relatively little benefit to plants, and you can have lights that benefit plants a lot with very low lumens.
> 
> I don't think anyone has made any PAR measurements on this light, but there's some speculation out there that it is similar to the Sat+:
> 
> ...


So, I'd probably be safe selecting plants from the low light selection on aquariumplants.com, right?


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## burr740 (Feb 19, 2014)

Lumens is relative to what people see. PAR is relative to photosynthesis. Having said that, 1850 lumens is fairly bright. But it all depends on how far away it is. Like for example the difference between having it 2" above a plant compared to 8 feet..

I agree with what matt said basically, but I think you'd have slightly higher par @ 16", in the 40-50 range if I had to guess


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## Argus (May 22, 2013)

burr740 said:


> Lumens is relative to what people see. PAR is relative to photosynthesis. Having said that, 1850 lumens is fairly bright. But it all depends on how far away it is. Like for example the difference between having it 2" above a plant compared to 8 feet..
> 
> I agree with what matt said basically, but I think you'd have slightly higher par @ 16", in the 40-50 range if I had to guess


Thanks. So go for plants with medium light requirements?


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## mattinmd (Aug 16, 2014)

at 35 (my estimate) to 40 (low end of burr740's estimate) You should be OK with low light and less demanding (easier) medium light plants.. hygro corymbosa, rotala rotundafolia, etc.. probably amazon swords, but I had poor luck with those, which may have more to do with my GH level...

I don't think it will go up as high as 50 PAR, but at that level you could grow any medium light plant that doesn't strictly require CO2 injection. (unless you're planning on doing CO2 injection) However, not a lot of people can manage to avoid algae headaches at 50 PAR without CO2.. fortunately the light is dimmable, so if algae crops up in a big way, dim it down some.


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## jorstrick (May 8, 2015)

I had one of those on a 55 did not do well at all but a lfs by me use them on shallow tanks similar to yours with fairly good results so I would say low to low-med light but then again I'm kind of noob 

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