oh yeah, even with the top of the pond covered in large floaters like water lettuce and hyacinth AND a 70% shade cloth over the pond itself which only receives 4-5 hours of afternoon sun, the water gets to 85-86 easy. Before the floaters and shade cloth i was hitting 88 on some afternoons. I have a large sponge filter in there, so the water temp is the same throughout.
As far as livebearers go, i would love me some variatus platies, or anything bright and good looking top-down! I don't have a lot of experience with livebearers, so any advice would be welcome!
here is a before and after pic of the pond which i started in May.