I think it's common to place a fermentor in a bath and rotate frozen bottles of water. Since I'm making my first ale with a hybrid yeast, I wanted to aim for even cooler temperatures. I opened an A/C vent in my unfinished basement and used a bed sheet to direct all the air onto my fermentor. With highs in the upper 90's and 100's this week, the A/C has been running frequently. Between that, and changing out the frozen jugs 3x a day, the bath temp has been staying between about 49°-59°F.