Cyclops are very little crustaceans, generally discovered in ponds containing daphnia. They’ve the appearance of having only one central eye, and it is for this reason that they’re named after the one-eyed giant in mythology.
These tiny crustaceans might be given to little fry fish just after the infusoria stage, but I think it advisable to feed only the larger fish with them. A double sac containing eggs in some state of development will probably be discovered on the end of the female’s body, and it is most likely these that the fish find so tasty.
Cyclops are usually netted in the exact same way as daphnia, but if a couple of are introduced into a shallow dish of water containing infusoria, they’ll breed rapidly. An old porcelain sink with the drain plug sealed, and sunk into the garden is an perfect container.