PetFish.Net Guide - Barbs, Tetras And Minnows

Another simple way to breed zebra danios is to just keep them in their normal
aquarium with the usual kind of gravel. Every once in a while one should vaccum the
gravel and let the water sit for 2-3 days. Lots of babies are then found in this water.
An added benefit is that all that gravel grunge will supply enough microscopic food
for the fry to eat for the first few days.