I can only tell you what plecs I have kept in groups and how it worked out. L260 by far does the best mixed with many in the tank, L110- The males beat the crap out of anything that comes near their cave. L399-Well that was an expensive mistake, female ate a smaller male. L134 Do ok, but if they don't have enough caves expect problems. L59, a BN so again the males are pretty rough on the females. As are all the other BN species I have in my sig. with LDA08 being the exception. The L030s are in a 75, there are 3 of them and they seem to ignore each other. The L001s fight with the L204s. And the watermelon royal beats the heck out of ANY fish that comes near it. She owns my 90 gal.