Phirana...

Who here has one/some?

My father wants to get one or a few. I know nothing about them and I keep reading all sorts of different things on the net about them.

Does anyone have a good / correct caresheet on keeping them?

I have kept red bellies in the past.

Beleive it or not, they are actually a boring fish. Not the eating terrors that you would picture a tank of these things would be like. I could put my hand in to clean the tank and move stuff around and never had a problem.
They will eat just about any meaty food offered but really like beefheart (you can get frozen cubes of it in a petstore).
I kept my group of 6 in a 125 gallon with a large pleco.
Some of the other species of pirahna are much more agressive and fin eaters and can't even be housed with their own types.
Check your local laws. A lot of states have now banned ownership of these fish (mine did or I would still have them).
All in all they are pretty nice looking and easy to care for fish.

A friend of mine back home had a tank of red bellies and a tank of pacus.

The pacus were more interesting.

Piranha tend to be finicky and not that hardy. If your grandfather wants a big fish that is interesting and is carnivorous I give a huge vote for Oscars. They are attractive, relatively intelligent as fish go and they are much more hardy then the piranha.

Just my 99 cents.