I keep 2 Green Terrors with my severum in my NW mixed tank and they're the best of friends, so it could go either way. Both Terrors I believe are female. One is about 4" and the other 6" while my severum is 8".
I have heard mixing green and red terrors is a bad idea but I have no experience with that one myself.
Happen to see groups of 3 severum living happily together a lot.
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