I've got silver sharks, 3 types of gourami,angel, congo tetras, yoho loaches and a huge plec (over 13" long) and not had any trouble with them at all. Not one nipped fin, no fighting and they all come together for food.
lol so did I. they take a while to chomp through lots of duckweed though that one of my tanks produces in enormous amounts, obviously because of the lighting in it. Day light and sunlight llight...well I assume thats why.
I was going to add my Firemouth in the tank this week , but having floated him in there and watched the two silver dollars going nuts I decided against it and left them where he is. I didn't want to upset the tank as its so calm and peaceful. Maybe if both had been younger it would of worked.