A little update: The room is already getting up to 82 during the heat of day. Last year it was very cool, but last year I didn't have lights, all the equipment, etc. The first step in fixing this was to put insulation above the room. If you touch the ceiling, it's warm. If you go into the attic and touch the drywall above it, it's cool. That means that heat is definitely leaking in from the attic via the exposed dry wall. I put in some R-30 attic insulation tonight. Wanted to wait for the attic to cool off.
I also need to address the window. A LOT of heat comes in through the single panel, cheap window that I put in. I fitted some insulating foam board to cover it today, but it only has an R-3 rating and I can still feel heat on the foam board. I bought some fiberglass R-13 insulation that's used for insulating walls. I'm going to put some behind the foam board tomorrow and sandwich it up against the window. It will look like crap from outside the window, but frankly, I don't care.
The heat wouldn't be an issue whatsoever were it not for the system I have on the wall in the fish room. My main system, which has the display on the inside of the house, stays a crisp 78 degrees all day. The secondary system on the fish room is getting up to 82 these days, and I don't want to push that much further.