I kept one, year later added the second - no particular conflicts, they stay together, but new was more active and dominant. Both started to have eggs on the regular basis.
One of them was more robust built dark red, good as cleaner for a fish, and another - slender elongated bright red, more interactive, reluctant with the fish. I had read, that this could be an age, but I tend to think that they are from different areas - none of them changed with age.