If wanting to try to breed the danios, then I would make sure they are the only fish in the tank, keeping them in their "group". If you see eggs, then you can move either the fish to another tank or the eggs to another tank... depending on how widely they are scattered. A pleco, shrimp, snails... will all eat the eggs as soon as they find them.
Most breeders of egg scattering fishes will keep the adult fish in a tank until they see eggs, then move the adults to another tank to keep the eggs safe until they hatch.
Another word of caution, be prepared to feed the fry, and flake foods won't do it. I would suggest baby brine shrimp, newly hatched, for at least the first few weeks. Be careful when siphoning it that you don't get egg shells mixed in, as your fry will choke on any shells they try to eat.
There are a few products on the market, powdered foods to be mixed for fry of egg laying fishes... be sure to keep the water quality extremely good, or the fry won't survive. This will mean frequent small water changes.