You would expect that the piranhas would leave the eggs…or start to eat them…the way other characins would behave. No!
The piranhas carefully inspect the eggs, eating a few which probably were not fertilized, and doing housekeeping chores to insure the eggs won’t be smothered or covered with debris. Actually they act more like cichlids (substrate spawners) than they do characins. The parents guard the eggs and viciously attack anything that comes near them. (I poked in a stick and they cut it in two…it was the thickness of a pencil…a chopstick.) In 56 hours the eggs have hatched and the young are still kept in the same area and guarded.
In about a week after spawning, the fry are free-swimming. The parents can be removed at any stage after spawning, but they usually don’t devour their spawn until they are at least free-swimming.
The fry can be fed newly hatched brine shrimp as soon as they are free-swimming. If you feed them sufficiently well, they will be an inch long in a month and capable of eating a dozen baby guppies a day.
The problem then becomes one of food. If you had a big spawn, you might well have had 7,500 eggs, and it is very conceivable to get 6,000 of them into the free-swimming stage. But what kind of live foods can you have for such a swarm? It would take a gallon of brine shrimp eggs to feed them the first week, then you would need larger shrimp or larger other live foods…and finally some baby guppies…or baby anything that swims and is smaller than they. After a month they can be weaned to beef heart (shaved, frozen and scraped), but don’t let them get hungry or they will immediately start to chew each other up. As a matter of fact that’s they way they usually grow, eating up their smaller brethren until perhaps a hundred or fewer are left, and most of them have torn tails and anal fins. Some piranha breeders have noted that the young piranhas have a great tendency to attack each other’s eyes, though their fins are attacked first.
The advantage of the kiddy swimming pool is obvious now, since you’ll need some place to store the piranhas until you’ve been able to sell them. Whatever you do, don’t throw them into your local river or lake! If you must dispose of them, be sure they are dead. Then put them into a plastic bag and burn them. I heard a story about one that jumped out of a tank. It was immediately seized by the family cat almost as soon as it hit the rug. The fish got the last bite and neatly took off the cat’s nose. Be careful!
-from
http://www.opefe.com/spawning_red.html
GOOD LUCK!
