There are 3 Vieja Synphilis living with the piranha, they try to color immitate them but get bit all the same once in a while. the only other piranha I have are 5 golds. The golds do not cohabitate as well with each other. They are just starting to color up some at about 3 to 4 inches. They seem to grow slower and bite eat other more often at least to this point in time.