I agree with Miss Wiggle. Depending on it's size, it will most likely be fine. Of course if it's a baby plec at only a few cm's and you put it in with a large cichlid, the cihlid might try to eat it. Of course, with it's armor, the fish might bite down, realize it hurts and never do it again... so in general, they should fine. And if anything they will grow an attitude of themselves to match the fish they live with. My common will gesture with my adult JD for position under my bogwood. The JD usually forces the plec out but it's interesting watch them quarrel for the same small space... and don't worry.. neither of them has ever gotten hurt from these quarrels.... usually consists of the Jd nudging into the plec and trying to push it out