Red b Piran.

im not sure about hte size issue, but i know some one that keeps oscars with there pirahnas. but the personality of pirahnas can be completely harmless to eat anything in the tank.

I wouldnt keep anything with piranha, well, that is, unless you want your decor to consist of skeletons. They are not the fish depicted in hollywood films, but that said they are also not a community fish. They should be kept in small groups a species tank, and 12ins is about the maximum they will grow - but of course you will always get those who go above the maximum. RBP are in fact quite a timid aquarium fish, so provide plently of cover for them.

You will be hard pressed to get a nattereri to grow to 12", but it is not unheard of. When I had just reds a tank, I had convicts, giant danios, and a blue gill living with them. When I added cariba to the shoal, they ate all the other fish that night. Reds will be skittish until they reach about 6" and then they are a great fish.