Commets and Shubs are prolific breeders. From one spawning from a large female you will get a multitude of fry. You can raise them successfully in tanks but they do better in larger bodies of water. Feed the newly hatched fry on brineshrimp then when big enough transfer them to ponds, or in you case, tanks with established daphnia. Once big enough they can be fed on trout crumbles. This is how I have seen it done while working for the largest goldfish operation in NZ.