Had a similar problem with our 65 gallon. Fine for a long time then, algae bloom! Couldn't get rid of it. 50% water change and next day it was just as bad. Finally invested in an in-line UV filter. Within a day or so it was clear. Some may see it as a bandaid, but there was no obvious...
The angels only bother other fish when they're protecting their half of the tank to spawn. Then it's just a quick "get out of here" chase.
I've never seen the beta near another fish, or any fin nipping. He just seems to mind his own business...
I guess my time with cardinals is over for now...
I am new to this forum, so please forgive me if I'm posting this in the wrong area.
I have a 65 gal tank (upgraded from a 29 about 4 months ago). It is a planted tank. The residents are:
1 pair of black angels (have spawned twice recently)
2 geophagus (surinamensis I think). They bicker...