78F is getting up there if you have rainbows. I have two surface aerators and my water is still stratified, at least I think, because all of the trout are down in 12-13 ft of water this time of year. How deep is the intake for the fountain? I can't imagine this could be the issue but maybe it is pulling cooler water from down deep ans bringing it up? Good luck and hopefully your water doesn't warm up too much more.
