Do fish only breed with the same species of fish?

In general, yes, fish only breed with the same species. This is because different species of fish have different reproductive organs and behaviors, and even when they can physically mate, their offspring may not be viable. However, there are some cases where fish can breed with other species, resulting in hybrid offspring. Hybridization is most common in closely related species that have similar reproductive strategies, such as damselfishes or cichlids.