I have a stars and stripes puffer and a porcupine puffer, They immediatly ate my chocolate starfish, and then proceeded to eat everything off of my live rock, and they keep it very clean still, I have always had puffers and I have never had a problem with them fighting or not getting a long, and you don't need a 500 gallon tank to put more than one puffer together. Mine is 150 gallons and they get along fine, I use to have two puffers in a 65 gallon too, and that was fine.