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Lighting for a 20 Gallon Long


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I know that the rule of thumb for MH lighting is ONE halide for every 2' x 2'. The 20 is about thirty inches long. I was going to go with only one halide until i saw some pictures of 20 longs with really bright centers and dark corners. That is what i don't want to happen. Should i just go with a higher wattage and hang it higher? or should i just get two 150's???

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Either would work, depends on what you want it to look like.


I have a 175w over my 20g long prop tank, and the sides aren't really that much dimmer. It is a SE bulb with spider reflector though, and I bent the reflector out just slightly on each end to better aim more light to the sides.

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I dont think you would want TWO 150 watters over a 20L. I personally have one 150 watter over my 20L and I get very good coverage. Of course it wont be as intense at the ends as it is in the middle, but this works well for higher-light stuff and lower-light stuff being in the same tank. I think it can depend alot on the reflector. I personally have the hamilton reefstar with a phoenix lamp.



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Trying to keep this bumped up. I'm trying to decide what to light my 20 with also.. Seems like alot of people have problems deciding what to use.

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I had a 250W MH light over my 20g long tank and this is how it looked. No dark spots at all.


But this 20 has gone down. So now I have that 250W light over a 40g tank.

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I'm worried about heat, as i'm not doing a sump with my 20L


Well I had that issue too but I used a very good and cheap method for that. Get your self a regular ghetto house fan. Let that air blast right across the water and you'll be surprised how much that temperature will drop. The only issue with that is that you will have some evaporation but you can stay on top of that and have no problems.

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