I'd second dolphins suggestion. Visit Planet Catfish and check out all the breeding articles. If you're referring to the 'Common Plec' (Which can be a number of species, Liposarcus, Hypostomus etc) then it really is quite impossible within the confines of an aquarium. These South American catfish are farmed in huge pools by the thousands in the far east for the trade. If you wanted to breed anything go for the Bristlenoses mentioned above and/or Peckoltia/Hypancistrus species. These need smaller setups and the breeding is outlined in the Planet Catfish articles. They are also much more desirable and sought after in the hobby so moving on the youngsters would be no trouble at all. B)