Currently we have albino, peppered, and bronze cories. The albinos are in my daughter's tank and the peppered and bronze in my son's, but at one time they were all together in a 20 (while I was moving furniture and tanks and such). They all schooled together without any trouble despite the colour differences. They are only seperated into colours now because of the colours of substrate that my kids chose... the albinos compliment my daughter's tank and the bronze and peppered cories compliment my son's. But, they did all school together at one point in time... the whole lot of them.
When we had just five cories, they didn't really do too much... once we had a total of eight cories in each tank they became really active and interactive. Just a thought but with a 55 gallon tank (especially a long) you could have a lot more than 5 cories.
The tetras I don't have a clue about.... tetras were one of my first mistakes in fish keeping... bought the dyed ones cause they looked so bright not knowing that they had been tortured to look like that. It certainly effected their personalities, they were like sharks with chum. I know not all tetras are like that but, after that experience I haven't bought any tetras.
