welll thats a good question ... they will eat all feeders at just about any size as long as tehy are hungry
waht kinda P you tlking about...cause most juv. P are fin and scale nippers so if still small expect that ... once tehy get bigger that tetra size tehn expext to see some nice chunks being removed from feeders
I started feeding mine feeders when they were about 1,25" in length. I started with neons and other small community fish (it's really sweet watching a mini-piranha chase a neon tetra :nod: ), and when they grew larger (about 2,5") I switched to goldfish and minnows.
well I still woulndt reccomend getting them feeders at that young of a size. they are more likly to make more of a mess and therefore causing your tank to be needed to be cleaned more often as well as it will not provide as much nutrition as "bloodworms" for example...and lets not forget that unless you quarenteen your feeders your open to the chance of parasites or other infections that may come by ... goldfish will carry diseases that are friendly to them but that are deadly to your P ... either way be careful
There are much better foods for your p's than feeders. Feeders are low in nutritional content and you also run a high risk of diseases. I recommend beefheart(promotes incredible growth, you can get it for less then a $1 a lb at the grocery store/butcher), frozen krill will give your p's great coloration, catfish fillets work well, and many others.
If you really want to feed them feeders then throw in a big lionhead goldfish. Its slow moving anf it will be easy for the piranhas to pick on. If your piranhas have suddenly stop or don't eat so much eating brine shrimp or bloodworms then its time for a big feeder it make sure they are ready. I would also go with large feeders instead of small ones because the small ones are hard for them to chase.
mdemers883: I agree with your food recommendations, but there's one little side-note I'd like to make: beef heart is indeed a very good food source, which stimulates growth, but not for very small p's. Because it contains a large amount of fibres, it may cause constipation in baby p's (since their digestive system is not fully developed yet). And this might kill baby p's.
SMTT: large feeders being shred to bits are fun to watch, but personally, I prefer somewhat smaller feeders, which are swallowed in one or two bites. It's not as brutal as large feeders, but there are no remains left to rot somewhere in a remote corner in the tank. Which means less cleaning/water changes to do.
Just my opinion, though