I have to stand by what I've said. In my experience, any cohabitation with Ps will eventually result in a tank of just Ps. I know there are keepers who have tried comms of Ps with other species and have had a modicum of success. And, you're keeping them in a comm for 3 years is definitely a feat. However, sooner or later, either by a missed feeding, by territorial male behavior, by simply getting spooked, or by accidental nipping during feeding the tank will eventually be a P tank. The only long-term success I seen has been through coming Ps with nano-species that would be considered as too small for a shoal of adult Ps.
Keeping Ps with another species for 3 years is something I've not heard of before in the 50+ years I've been in this hobby. I hope you can keep a running report on the conditions used in this arrangement and the maintenance and attention needed to keep this arrangement going. And, I hope that should this co-habitation end unpleasantly that you'll inform the membership of that event. This situation is not the norm for piranha-keepers and I don't wish readers to get the wrong idea that such an arrangement is recommended to attempt without proper pre-planning and meticulous attention to maintenance.
