Ah ok, my wyckii just battered fish of any kind but didn't kill much even at 22" I could keep fish over 6". Nemurus are alot more mellow and rarely pass 12" so I should be ok... I hope!-)
What TBTB was trying to get at, and me supporting the possibility, was they may not like each other. However it seems to be going good for you so far.
And as far as wyckii being killers, I found mine to just be protective of its hide and the area right outside of it. Other than that, at night when it was swimming, it only bothered my sun cat and Trachy when they ran into each other. The sun cat asked for it trying to pick a fight though. I didn't see if the Trachy did so but wouldn't doubt them fighting as well. The Trachy definitely didn't let the wyckii in her hide though. I think it's just wyckii have a strong bite so they have a good potential when it comes to ending another fish. And they don't back down from a fight, they don't mind starting them either. Definitely not as bad as wyckioides imo. But I only had one of each.