theoreticly yes.in practice no.piranha arn't super violent fish by default.they are nervous,shy fish though and they feel best in a large school.now the arawana,thats a huge onery fish too.so these fish together would need a tank around 500-1000 gallons(thats a bare minimum) to make enough room for both fish to have ample space to live.then consider the fact that you will need a constant supply of small feeder to keep the hungry piranha from picking at the arawana.and that still doesn't make and promises.are you still interseted?