MH over a 20 gallon...

[X-Treme]

I think I might actually get a custom tank made to better suit the light because the light is 15" wide. I am thinking a 24"L x 15"W x 18ish" deep (need a DSB for my yellowhead jawfish). And BTW the lighting is 10000k and it comes with two colors of actinics. 2 24 Watt t5's of each color(420nm and 460nm)

[midgetwaiter]

That simplifies things then. Somebody with more SPS experience may correct me on this but I think you could go with either unit and be happy.

The 250 would give you the option to put your high demand critters almost anywhere where with the 150 would still require a bit more planning and be less flexible. Really fussy stuff would still want to be high and centered. On the downside with the 250 you'd have to be careful with acclimating new additions and some things like zoas and mushrooms would be difficult to place.

[imisky]

what size is "small" in your opinion, because clams that are 1-2" does not depend on light as much as they depend on live food as there mantles are too small