Hi there
Bought a AP 24 w/ the 150W MH lighting. Might came with a glass top, it cover the front part of the tank (where the light is to avoid water/salt spraying onto the light) and leaves the filtration (back) part open. I am still in the process of setting it up but, I've been asking around and what I been told is that the
Metal Halide lights should NOT be a problem w/ temperature. I'm going to keep mine in my room and it's pretty small. I've got a fan on the ceiling, but I am still worried about the lights heat. Trust me the MH lights get pretty hot!
I do think that if you added some kind of fan around the area where you place the tank it would help.
Good luck to both of us!