guppies... if you are asking SW fish probably Occellaris clownfish (false percs) or maybe neon gobies. THe issue with breeding any SW fish is raising very small food as many fry will only take live food such as rotifiers. Bangai cardinals and seahorses are known to take baby brine shrimp which are considered easier to reliably produce than rotifiers or plankton. It is my advice to get considerable experience both keeping marine fish and breeding first livebearers and then egg laying FW fish before attempting any SW breeding. JMHO
