corvettecris;174945 wrote: Yes, open top. Unlike Mark, I have zero heat issues so far. Mine doesnt receive any direct and very low ambient sunlight. I believe Mark's is near a window? I have the 150W disco ball and it is working great. It actually packs a nice punch, and I am keeping a maxima on the bottom with no issues.
I think even a 250w is a little overkill. I have talked to 2 people that have used 150W's successfully on tanks about the same depth (20-24"). Darren is one of them. With a good bulb, they were getting excellent growth of everything. I think with the 150W you will have lest heat issues, and you'll be able to keep everything you want.