Try Exodon Tetras .... I have 12 in with my eight P's and have never had one come up missing. I think they are too fast for the P's to catch. They also add some excitement at feeding time. My Exodons will attack feeders before my P's.
you can cohab anything with serras. or pygos but eventually it will get eatten. If its a large piranha you can try small tetras or so,there to quick for large piranhas so they dont bother trying to catch them
4 red belly in 75 10"
i had 6 3.5" bucktooth tetra with 12 piranha since they were 1"
they started eating them after 10 months
the bucktooths were in the tank first
blue gill caught out of pond might work if out number piranha.im tryin 9 bluegill 3.5" havent seen any problems in 3 wks at same time added 4" african cichlids 3 and they ate 2 and i feed every day once a day