I've had rosy barbs with angels since I got the tank going in January, and I've never had a problem with my angels getting their fins nipped.* * The barbs pretty much just keep to themselves...Jerry just happened to get in the way of one of their swimming frenzies.* He's acting perfectly fine, and everything looks all right, except for the position of his fin.* Nothing appears to be torn or anything, and he's functioning fine.* It's a 29 gallon tank, and besides the 4 rosy barbs and 2 angels, I have a few tetras and a pleco.* I don't have a test kit yet, so I can't give you readings.

** I don't have a set schedule for water changes, but I'd say we've been doing about 20 - 25% every 2 or 3 weeks.
I keep the tank clean, I've got a good filter for that size tank (AquaClear 110).* My water is nice and clear.