A few years ago I found out by accident that running my diffuser 24/7 was not a problem as warming of the trout pond was insignificant. Found out because I forgot to shut if off at night a few days in some really hot water.

Keep in mind my trout pond is quite small (1/10th acre), very steep sided and received 51.6 F. well water at ~ 45 gpm 24/7.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.