Thanks for the suggestions. I was concerned about the temperature too but I think it will warm up enough if I restrict the flow. There is no way that I can run the pond water into the basin.
What we have is an old pool/trout pond that my father drained 45 years ago out of fear that one of us kids would fall in and drown. The concrete structure is still there but it is in such disrepair that it would be a major project to fix.
