I kicked all these ideas around, I just ****ed away time. How big is your fishroom? I was using a 5K BTU window unit & it sucked. My tank would sit at about 82-83, I did not like this because summer had'nt even hit yet. I said screw it, I dont want to buy a 1200.00 chiller. I went to HD & picked up a 18K BTU window unit, hooked it up & the tank has not gone over 79. I keep the elec. thermostat at 73. This keeps the tank right so far. I run my fuge on a reverse photo period, doing this I think keeps it stable.
My system is right at 300G. The tankroom is about 110Sqft.

Also the room is nice & comfy. If I had to sleep in there I would be very comfortable. So far I hav'nt had to! :-D The wife is being nice & has'nt kicked me outta bed; YET!!!

My point, Sorry. Try the A/C by itself first, that is alot of water. I dont feel you will have any heat issues. I dont.