I have in the past placed frozen water bottles in my refugium, 2 or 3 in a 55 gallon they last for about 30 min to an hour but it helps. Turn lights off, have fan blow on water
i don't have the reef running right now... but you don't have to have your AC to 72 degrees... LOL... my ac would always be at about 78 and keep the tank at about 80F... even during the cold times, i would keep my water hot... around 80F constant...