Yeah, they would look great in a pirhana tank! Especially if you let them clean the bones themselves.
I'm going to post some pics as soon as the tannins clear up a bit, it's kind of hard to see clearly right now.
My adventures in keeping Indostomus crocodilus, the crocodile toothpick fish. AKA armored stickleback, paradox fish, and freshwater pipefish. Care is (to the best of my knowledge) exactly the same as Indostomus paradoxus.