I think that's why they suggest the floating plants. It shades the water a bit and helps keep it cooler. But if you had filtration moving through it I think it'd be okay. I've watched a local guy raise tons of severums in vats which are in a greenhouse, and in the summer you'll start pouring sweat the second you walk in. I was there in October and the temperature in the greenhouse was still over 100F. Yet the fish are all fine.