It costs the same amount of $ and energy to breed nice fish whose genes should be carried on as it does to breed pet store fish that were sold to be pets as opposed to breeding stock. I would suggest you find a quality pair of halfmoons or crowntails from a breeder to work with. It basically comes down to the difference between breeding two random dogs of unknown mixed parentage versus breeding purebred dogs. In the first case, you could end up with puppies that look like anything, and could have any temperament. In the second case, you know exactly what you'll get and you have papers showing the parentage for several generations, making the puppies attractive to other breeders or people who want a specific breed of dog. Those puppies sell themselves, because people seek them out. In the case of fish, you can sell them online when the offspring are from a line that breeds true, and people seek them out. You want fish that people seek out because it makes everything easier on you, and it means your fish are more likely to end up in homes with people who know how to keep fish happy.