Fish will attack the glass because they see their reflection. Sorry, that is really obvious, I am sure you know that.
Therefore, the best way to stop them from attacking the glass is to make sure they don't see their reflection as much.
Think of the tank as a house, and now think of your house. During the day when it is bright and sunny outside, you dont notice your reflection in your window. At night, with the lights on, your window practically becomes a mirror.
Therefore (if you arent already doing this) if you make sure the room that the tank is in, is well lit while the tank light is on, your angels might not notice their reflections as much. This works with my betta. When the tank light is on, but the room light is off, he gets very angry at his reflection, but with the room light on also, he doesnt even notice.
As far as preventative treatment I am pretty inexperienced with medicating fish. I'm very interested to hear what people say about that. I hope your angels feel better soon!
Last edited by Public Alias; 10-18-2012 at 04:37 PM.