@newmag1659 Killifish are really no different than any other tropical fish. Their breeding habits are a bit different. They lay a few eggs almost all the time rather than one large spawn all at once. There are two very distinct types. One type is the true annual like the African Nothobranchius group and the South American Austrolebias which includes the Argentine Pearlfish. The true annuals are all soil spawners which deposit their eggs into the substrate. These eggs lay dormant when the temporary pools they live in dry up and then hatch out the next rainy season.
The other type includes Aphyosemion, Fundulopanchax, Aplocheilus , Epiplatys and others. These are all plant spawners and have life spans similar to a Betta.
All Killifish are extremely colorful and rival many marine fish. The tank you describe sounds perfect for any of the plant spawners. Fundulopanchax gardneri are a good fish to start with but I must warn you about something I learned the hard way. Males are very hard on the females. The spawning urge causes them to drive the females to exhaustion. There are two remedies to this. If you use the artificial spawning mop method of breeding keep the sexes separate and put them together to breed for a day or two then separate them again. If you prefer to breed them in your planted tank then have three males and four or five females. The males will spawn with the harem and they will also rumble with each other for territory thus giving the females a break. Resulting fry can be scooped out with a turkey baster when they appear. Fry raised this way are said to be more robust and healthy. Also, less work. Another very easy Killifish to breed is the Golden Wonder (Aplocheilus lineatus). They get over three inches and can be quite predatory. Most Killifish can be kept as community fish but I prefer species only tanks as it seems to make natures way easier. Good luck.