Cyclops are tiny (1-2mm) copepods that swim in a jerky motion; they're related to Daphnia and are a bit smaller than they are.

People that culture live food prize these highly as an excellent food for small fish or fry. There is anecdotal evidence larger Cyclops have attacked the smallest fry so be forewarned and use caution, you'll see references in (especially German) literature to "sifted Cyclops" as fry food.

They can be cultures quite easily in the same manner as Daphnia.

They eat green water (and a large cloud of them will denude a tank in no time, although Daphnia work better) bit will also eat prepared food.

Put a tablespoon of high quality activated carbon in a blade (not burr) type coffee grinder and process for a minute to clean it. Wipe it out with a paper towel. Not put in two tablespoons of rabbit pellets (alfalfa) and process till micro-fine.

You used to have to pay a few bucks to buy this, it was called "Hobby Microzell" - 100% micro powdered alfalfa - which came from Germany. Certain bugs such as Daphnia, Cyclops and larger Artemia (brine shrimp) eat it outright while it also provides safe bacterial growth for feeding animalcules such as Amoeba, Paramecium and the like, pure cultures of which are good to have on hand for raising fry.