My tanks last winter dropped into the low 60s. the gar looked amazing.. my aba knife had no problem with it 'nore did my eels. key is a slow drop.. and the steady temps.. just like they would see in the wild. I wouldn't let them get much below 62 for trops... and remember ick sometimes can get a foothold in the lower temps, so any signs and ide bump temps back To the 80s and try a slightly warmer temp if you decide to drop it back down. had this happen with our fahaka puffer. increased the temp back up, water changed the gazungas outta the tank for a few days and all was well.