I would go with 250 watt. A 400watt might heat up your tank a bit too much and I don't think it is necessary with 20" high to have more than 250 watt. I have 250 watt and have very good results with my SPS, even in the middle of the tank and mine is 24". The fact that I have 250 watt also let me put some zoanthids at the bottom without burning them up.
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More fish die from human stupidity than any other disease...
Last edited by daniella3d; 12-12-2011 at 07:41 PM.
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