Tagging along as i HAD this problem. I have a 135 that was given to me...friend moved and did not want to take to California from Texas. Been hotter than...well you know....here. Anyway, i have a 30g sump which had a Mag 12 in it. Also had a few Rio's for powerheads (2100's, 1100's). Tank is in room which is on the far end of my a/c vents. Temps with a fan over the sump, open tops, PC lighting with the legs on it (raised above the tank about 4"), and it was hitting 85-87 during the day and not much lower at night. I first started by taking the wattage hungry rio's out and going to maxi-jets (now have seio's). Then i moved the mag 12 out of the sump and run it externally. Doing this only got the tank down to 85 during the day. I then put a window unit in the room...which blew right under the tank by the sump. This got it down to 82...which i was happy with.
Well then i got my first electric bill. 358.00 :eek1: . So i searched around the local marine site and found a used chiller. Set me back a mere 125.00 with the pump (JBJ artica 1/10hp). I figured what the heck and their site said it would work on the tank...i know a little small but i figured if nothing else i would put it on a future smaller tank if nothing else.
I now have it set to 81 and from what i have seen it only comes on a few of times a day. Piece of mind is now with me again, and i can enjoy my tank instead of constantly battling with the temps. We have long summers here in Texas and i must say this has been the best investment i have made to date.
I would look into the power consumption of your powerheads and anything else in the tank which could produce heat. Try to run any sump pumps externally if possible. I will soon be putting the chiller pump externally once i get the sump or tank drilled with a supply. Good luck to ya, and if all else fails...look for a nice used chiller or spend the bucks up front....piece of mind and not having to constantly fiddle with the tank has made me a happy camper once again.