It’s a nano fish from India called Dario Dario or scarlet badis. They are mini predators that only eat live food (mostly) and are otherwise not too difficult. I would say keep an Eye Out for the fruit flies and neps. In the past I have killed hairy hamata and even now I am dealing with hamata issues due to mites that tend to take over fruit fly cultures. I almost killed the hamata (it is a very rare form) and luckily it seems to be coming back. When you say collembola is that globular springtails? If yes I would love to get a culture from you. Those are so awesome and cute.Nice! I don't think it's unusual to keep feeders for specific pets. I'm working on getting back into keeping dart frogs (kept them many years ago in high school) - it's my pandemic project. That will mean a surprising number of feeder colonies: fruit flies, crickets, collembola, isopods; plus I am contemplating trying to grow pea aphids (which I'll then have to figure out how to keep off my plants) and even starting an ant colony (which has entertainment value all on its own). All just to feed some finicky little toads.
I will say, that's a nice looking fish though! What is the fish? Some type of cichlid?