I have been asked to make up a little post about piranhas, well I have 2 P nattereri (Red Belly Piranhas) I bought them about 1-2 years ago and at the time I really didn't know that much about them, the people in the shop told me they could go with my cichlids and so I came home with 2 piranhas the size of a 10p coin, I added them to my tank and after a few days I noticed little bits out the cichlids fins, well out of many of them so I moved all the ones that had been gotten and there remained one severum who lived with my piranhas for about a year, by which time they had gotten about 5" and I finally moved the severum when a little bit of his lip was bitten off (it is now fully healed) now I have some small (and fast) tetras in my tank.
now that is my story of my piranhas.
now a little piranha info:
piranhas mainly come in 2 Genus in the shops around the world, although there are in fact 4 that I am aware of.
Pygos (Genus Pygocentrus) are known for there rounded look (like red bellys) and these 3 species can all shoal, in fact that is how they like it, the most tolerant of all these is P nattereri, if you wanted to keep other fish with piranhas these are the only ones you have any chance with.
Serras (Genus Serrasalmus) are more pointy than pygos, this genus includes the black piranha (Serrasalmus rhombeus) which can reach 18+", it also includes the small but beautifull Serrasalmus elongatus which has a max size of only about 9".
This Genus is known to be very aggressive and intolerant of even its own kind in the cramped conditions of the home aquarium.
However there is one or two of the serras that will shoal like Serrasalmus geryi which are known to do best in shoals.
For more piranha information - please click here