We recently had a crisis with the fish in our pond. They disappeared! After ruling out a multitude of problems we are very sure it was the water temperature and in fact, the fish were hovering on the bottom of the pond, which is about 2.5'. We have used various remedies (running fresh water into the pond, dropping ice into the pond, and, putting a beach umbrella at the end of the pond. Still the surface water often hovers around 82 degrees and one day it hit 92 degrees.
Is there anything, beyond what is mentioned above that we can do during the summer? Of course we are adding as many plants as we can as well, but it is a new pond so perhaps as we get more, we will improve the condition.
The fish seem to be doing fine, we just don't see them as often and wonder if there is any serious threat. Ellen
Goldfish-water temperature, etc.
I have goldfish in my house and it frequently reaches 80 degrees. I usually turn the air on if it is more than that. They do not even seem to mind it at all. I do not notice any change in their behavior or activity. With your pond being 2.5 feet deep, it will be notably cooler in the bottom than on the top. Of course, that may depend on how your water is being filtered. if you are drawing cooler water from the bottom and then returning it to the pond at the top, that will create a 'current' where the cool water will mix pretty well and then the bottom will not be able to stay cooler, I would think. At any rate, 90 ish is pretty warm, but I wouldn't be too concerned just in the 80's. You should have rocks and plant cover for the fish to have shade. The main thing to be concerned about is the oxygen level. The warmer temps can cause lower oxygen levels and that will cause the fish to slow down activity alot.
You could try agitating the water more to fix that.
You could buy an air pump and stones - that would probably help with the stress. When I had a smaller pond, we used to freeze water in 2 liter soda bottles and put them in the pond.
I think trying to cool the water would be hard on the fish, as the temp would be fluctuating up and down and make it hard for the fish to keep adjusting to.
If the pond is shallow and you suspect temps to be too high most summers, you should think of building a trellis, arbor or something around a side or two to offer some shade.