I have a 30g 3' community tank. I have 2 angels, 4 emperor tetras, and 2 dwarf neon rainbows. I know rainbows are schooling fish, so I would like to get more, but I am concerned about over-crowding the tank. Do I have room for more rainbows, or would I have to get rid of some of the other fish first? Also, is anything unique required as far as caring for the rainbows goes?