Aside temperature issues with subtropical
Channa it depends on the individual fish to a great extend if socialization is possible. Also the way you raise/keep the fish (always alone, always with others, etc.) can be important, imho
.
I had a
Parachanna obscura (it's the one in my avatar) at ~48 cm/~19 inches that was with community fish through all the 18 years I got her, bought at ~8 cm/3 inches in 1994. She was very suspicious against other fish, agression occured only when she was threatened. There was only one fish that she would not accept , that was a ~40 cm/~16 inches
Hemisorubim platyrhynchos that I had to take out of the tank.
I own a
C. marulioides since december 2010 that is currently at ~70 cm/27,5 inches big and that has always been with community fish as well. Got her at ~15 cm/~6 inches and she was always with other fish like the
Parachanna was back in the day. She's more of a brute and did sort out (I took them out, no one died
) some tankmates in the past, but most fish were ok and were completely ingored.
Now I introduced two quite big
Clarias batrachus-catfishes into the snakehead-tank and she's ok with them, but not in in every part of the tank which is a bit weird since she don't hold a territory where no other fish are allowed normally. But even there the
Clarias only get nipped gently without injuries. Even two tiny (~28 cm/~11 inches)
Polypterus endlicheri were in the tank for over half a year without any problems, those were observed closely but no harm in any way was done, not even nipping when I introduced them.
Anyways, when I set up my new 291g I'll introduce the catfish a few days before the snakehead so that she'll arrive last in the tank, I'm sure this way she'll be more compatible with them through a "environmental reset"; this worked out for me with a bunch of fish through all the years I'm into fishkeeping
.
As a note, if you keep a snakehead alone for a longer period of time OR you add new fish unknown to the sankehead to your tank where the snakehead lives for a longer period of time and has it really settled in the chances of aggression and incompatibility are greatest, from my experiences.
The "keep snakeheads alone"-rule does not work well for my fish I had and have, especially my current
marulioides was quite shy in the short periods of time when she was alone.