LED Fixture: Distance to Water-How Low is TooLow?

Reef Frog

New member
I'm designing a custom low profile semi enclosed hood for my next build. I want to stay under 6" height if possible for aesthetic reasons - the lower the better.

I will probably go with a high(er) end LED fixture like Ecotech, Kessil etc which are very thin but am not decided yet. I'd like to get the lights as close to the water as possible without any operational difficulties like over heating, excessive salt crust on the lenses, damage to the fixture, light spread or other problems I'm not thinking of.

Almost all of the photos I see of LED tanks seem to have LED fixtures mounted high. Why is that? Is that the only way to go?

Since intensity & spectrum are intimately adjustable, I'm assuming that "burning" stony corals isn't an issue, right?

The closer I can get them to the water, the thinner I can make the fixture. I think a Radion G3 fixture is less than 2" thick...would 3-4" off the water be OK or am I asking for trouble with this idea? What's the minimum distance I can get away with? And what compromises am I making regarding light spread in a tank with a 4'x2' footprint? Thanks for any ideas.


New member
Anthing with tightly packed clusters is going to be problematic so close to the water line because of coverage issues. I think something linear without optics would be your best bet. So something like the evergrow fixtures, without optics (120*).

People tend to hang them high to get good spread since a lot of fixtures seem to use optics that are 90* or tighter. Color blending is the other issue, with them very close to the water you will get a lot of spot lighting of individual colors. I personally have my LEDs 12" from the water line to help combat these very problems and mine have "wide" 90* optics.

For your low profile situatuion T5 might be more suited to your build. Splash guard will keep them clean.

You could also do a DIY but the heatsinks don't tend to be low profile. I would use the multi LED stars, such as the ones that have 2x RB and 1x NW from led group buy because they will help reduce the color blending issues of them being so close. then you can pepper in some of their special "OCW" stars to fill in spectral gaps. But it still leaves you missing the 420nm spectrum so you will need some violet diodes as well. So when it is all said and done.... again T5?

Reef Frog

New member
Thanks for the response. I understand what you're saying about spread. Lots to consider especially the non blending/spot lighting of some individual colored lights. Never entered my mind.

I'd go with 120 optics for sure and would buy enough fixtures for the entire length. Don't care if I have run them at 10%. I can handle all cooling issues by having the toos of the fixture exposed to the outside, fans or both. I know it sounds like a waste of $£$ but I'll do it as I want something like the Radions controller package - and heck it's a one time expense so I'll go for it.

Your idea of linear vs the round puck format is excellent & makes sense. But it seems like the pre-built linear or strip units are all low 1w power, no or little multi spectrum capability, limited on custom settings & programmability. The picks have all the flexibility but maybe I haven't IDed the right linear format product yet?

Dont want to do a DIY on the lighting. T5 is excellent. Have them now with good 5 year success. But this build is LED but I guess hybrid is possibke too. Ah, lots of decisions.

Thanks again. Anybody else? How low can I go?

Anything, anybody else.