I have to worry more about the water getting too warm than too cold. I have a horse trough pond on the roof and it gets into the mid 90's in the summer. The Mollies and Guppies seem to handle it fine. The pond in the picture above, what I call the garden pond, is fairly deep to keep the temperatures more moderated. It generally goes between 75°F in the winter to 85° in the summer. The inside pond stays fairly even at around 78°F. The garden pond and the inside pond are made of concrete and our water here is naturally high PH so that also limits the type of fish I can have. I'd love to have some Discus but they need lower PH. There are many types of Angel fish these days, I have seen some of the silver ones that are quite gorgeous. I'm hesitant to add any fish to my established ponds, I don't have a place to really quarantine them for a long time and I'm afraid of new bacteria. So, I'll probably just admire the silver Angels at the fish store.
