Two days ago I purchased 5 rbp (3/4-1") from a LFS. I acclimated them and put them into my smaller tank with some zebra danios. I few hours later I noticed zebra danios as well as rbp with really bad nipped fins, but I knew this would happen. What I didn't expect was the larger of the five rbp gouge out the eyes and eventually kill 3 piranhas. I only expected to lose maybe one over a period of time not 3 within 4hrs of each other. The next day I went back to the LFS and told them what happen and purchased 3 more rbp. After acclimating them I released them into the tank and immediately the aggresive one starts biting the 3 new piranhas and they all have a big scuffle. I then removed the aggressive fish and moved it to a nursery. After monitoring the new rbp I believe that the LFS may have sold me black piranha Serr Rhombeus or the other Serr piranha from venezula (i forgot name). The aggresive piranha doesn't have the juvenile black spots on the back like normal rbp. Anyway, pics coming soon