need some advise for my fish

[michael p]

today on christmas eve i have went to a pet store to get me another sun catfish the one i am currently raising is still young and i got it a week ago so i put the one i got today in the tank and immediately the sun catfish i have was not happy and they were both fighting. the one i have had for a week is about an inch bigger than the new one and the smaller one is now pressed its self in a small crack

[Viktor Jarikov]

That's not surprising and could even be expected. The size of the tank and the furniture matter, as does the fish size. Sun catfish are schooling fish but they have an hierarchy within the school, therein the aggression is diluted. With two it is most usually a problem where the bigger will always bully the smaller. Three are a bit better but still risky. I'd think 6 is the smallest number if one wants to minimize relationship problems.