Kessil a150w on a 5 gal

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It might but you would get a massive ring of light around the tank. Look at it this way, I have seen guys running 6 food tanks with 4 sometimes only 3, 150's. It's a beefy little light. If you already have one, worst thing that can happen is you try it and see if you like it and if it works out. If you don't and are going to buy one, save your money and get something smaller.