As the only fish we have ever bred are live bearers (Mollies & Guppies) I'm definately no expert (with them the big question is how do you get them to stop breading ) But I think it depends on the species you would like to breed. From what I have been able to find out each species have different conditions and triggers to enduce breeding. Some will breed with a change in diet, some with introduction of brackish water (species that live in fresh water rivers but get a rush of brackish water from ocean tides) while others may have their breeding triggered with a change in tempature.
If you could narrow down what species you were thinking of trying to breed you may get more responses.