How do you tell if a piranaha has laid eggs? Or is going to?

Question

I have 4 piranahs and 1 of them seems to stay hiding in the plants in the tank. Its always the same fish and it is always in the same place.

And this just started recently. The other 3 seem to move much more freely around the tank.

Answer 1

Piranhas spawn like many of the SA cichlids and NA sunfishes.  They "dig" a depression and spawn in that.  Then the male, or both parents, will watch over and protect the eggs.  This is not normal behavior for fishes of the Characin family, but it works, so why not.

So, if the hiding piranha is hovering over a depression in the substrate, check closely.  You could find eggs or fry.