For what it's worth, my water has a ph of 8.2-8.3 and a kh of 18 (give or take a couple points, I don't remember exactly). I've got angels in two different tanks that seem to be happy and healthy. They've been in the tanks for a good long while and spawn regularly. I also have gold rams doing the same. I think the majority of fish will adapt to the conditions. If you can find fish raised in more alkaline/hard water, they'll adapt to what you have a lot easier.