I was thinking of buying a new 55 gal. tank. It comes with 2 red bellied piranhas. Will this be over crowded?

Yes it would be overcrowded as these fish grow to around 12 inches and need to be in shoals, so a tank of at least 100 gallons would be needed.
What are you going to feed them?

I was going to feed them tubifex worms,blood worms,shrimp ,feeder fish and just about anything elese that I could find that they'd eat. Oh sorry I just realized that I posted this in the wrong section could somebody please move it? Thank you

Not a good idea, I'm assumeing the pirahna are red bellies? If so you would be hard pressed to keep two in a 55g. Not impossable but very difficult, they can grow anywhere between 8 and even 14". Even if you were willing to do the work it would take to keep two together it still wouln't be a good idea, red bellies need to be kept in larger shoals, with only two one might kill the other. They would also feel less comfortable and act more nervious. Though there is a certain appeal to keeping this fish they also really aren't all that interesting. If you have ever kept silver dollers or any other member of the tetra family that pirahna belong to than you will already know what to expect. Not kept properly they will tend to hide or dart around nerviously. Due to their dietary requirements they would need a lot of tank cleanings, don't forget that your hands would have to enter the water with them to do this. Though bites are rare they do happen and they will hurt.

well, i would say around 50 gallons per fish. Plus with their diets would require lots of tank cleaning.

plus my dad had a friend who was cleanig his pirahna tank and one bit a huge chunk off of his finger. he had them seperated with a divider, but pirahnas will do anything for food and one jumped. Its kinda gross looking at his scar

try pacu. just about the same thing. but legal.
haha... theyre correct about the gallon requirements but it would be cool to have in a big tank...

NO!!!! VERY BAD IDEA!!!! Pacu are worse than pirahna for one single reason, size. Pacu can grow huge, larger than a man-hole cover. You would need a something over 300g for just one of these.