Yes, they can take 75 degree(F) water for short periods(days) as long as the water's oxygen content is maximum capacity. You can use bubblers, powerheads, and HOB filters to keep the water surface moving and maximize the oxygen content. To a certain point it's all about oxygen, not temperature. Obviously though , if you can keep the temp. down, the oxygen level will be higher. If you can keep them closer to 68-70 and don't overstock the tank they will do just fine.