Back when I had my 46 bow set up, I had an Angelfish. I purchased him when he was very young around when I actually first joined the forum here.....and two years later he was MASSIVE. He was a really fun and interesting fish, very attentive and curious and smart....I had to train him not to bite me when I did water changes though. xD
He was a decently active fish though, quite literally RULED my entire tank. Personally, I don't think a 20 tall is large enough....something like a 29-40+ gallon I think would be much more ideal long-term.
Also, though I'm not sure of the exact hardness level, when I had my Angel I lived on hard well water with a very high PH. He seemed to do just fine, always bright and colorful, never had any problems.
Thank you! I have very hard water here, so I was wondering if that would be a problem. I was at my lfs yesterdays and a 20 gal does look pretty small. I wouldnt want a community tank though, just one pet angelfish :). Everyone seems to have a different idea of their max size lol, but from what I think a 29 gallon should be enough room, right? Maybe even a 25 gallon? lol idk...
I don't think the hard water would be much of a problem. Most common fish species bred and raised in captivity, to my understanding, can generally adjust to different water chemistry's just fine....its when you get into the more sensitive and wild-caught species that you have to start worrying about your PH and hardness and whatnot.
Have you posted anything on TFK yet? I'm sure there are much more experienced and knowledgeable Angelfish keepers over there that could give you a bit more info. xD