I've got 2 Jaguars in with 2 Piranhas and 3 Plecos. Jaguars are a very aggressive fish. When I put in the feeders the Piranhas will dart at there prey grab them and rip off little pieces until they are done. Whereas the Jags will open up there enormous mouths, take in half the fish and usually take the head or tail right off spit out the rest and repeat until they are finished. That is only with the larger feeders. The smaller ones the just swallow whole. My larger Jag is finally starting to develop his fangs and I'm very curious to see if this changes his eating style. Oh yeah, my Jags are definately the dominators in the tank with the Piranhas. If the Piranhas get in their space, the Jags put them in their place. So far so good!