N. albimarginatus is what I would call a basic Nothobranchius. Body coloration is silver with some blue iridescence and scales are edged in red. There are some red vertical bars on the caudal peduncle and the tail is bright red. Anal and dorsal fins are yellowish with red markings and a narrow but bright white marginal band. This coloration is very similar to all members of the Nothobranchius guentheri-group.
One or two pairs of this species can be kept in a 5 gallon aquarium. I prefer large breeding groups whenever possible and keep a number of fish in a 20 gallon tank. Males spar and display, but damage is rarely done. Water changes of 50-80% are carried out every week. Salt can be added at a rate of 1 tablespoon per 5 gallons of water, as Nothobranchius are often susceptible to velvet.
Adults are fed a variety of foods including blackworms, frozen bloodworms, grindal worms, frozen shrimp, and baby brine. They are not picky eaters and have good appetites but don’t like flake or other prepared foods.
Breeding Nothobranchius is a completely different endeavor than you may be used to. Being annual species, they need a substrate to deposit eggs into. In the aquarium, we typically use peat or coir. Getting them to spawn is pretty easy. If they adults are well fed and the water is clean, they will spawn. I personally use a plastic container of some sort (usually a small deli container or margarine tub) with coir. The adults will spawn in the dish and after spawning you can remove the peat, squeeze out all of the water (you won’t crush the eggs, squeeze hard!) and check for eggs. They’re pretty easy to find once you get the hang of it. If you have a good number of eggs, place the peat in a plastic bag and into a stryo box for incubation. Incubation temperature should be in the mid 70s. Usually incubation takes 2 months but may be more or less depending on temperature and moisture. It’s a good idea to check the eggs every few weeks to make sure they aren’t too dry and look for development. When you see eyes looking back at you from the eggs, you know it’s time to hatch them.
For hatching I will usually put the peat in the same kind of plastic dish that I use for spawning and fill it with water. The fry will all hatch within 24 hours. Once the fry are hatched and the coir has settled I will SLOWLY lower the dish into a half-full 2.5 gallon tank with a sponge filter running a light stream of air. Fry are free swimming shortly after hatching and eat newly hatched baby brine shrimp almost immediately. I also use golden pearls and microworms as the fry are somewhat small. I find offering foods smaller than bbs has been beneficial.
Fry growth is quite fast and first signs of sexing out can be seen at 6 weeks. Males often grow faster than females, so separating the fry as they grow can be beneficial. Another reason for separating the fry by size is often I’ll get a few dominant males that will slow the growth of other males. Eventually as the fry mature they all reach a similar size and I put them back into one tank.
Nothobranchius albimarginatus is a beautiful, prolific, and relatively easy species to keep. It’s a good first-time annual fish as the incubation time is short and the fish are pretty easy to keep. Annual fish do take some extra work and the fry can be harder to raise than other species, but their biology and life-cycle are pretty fascinating.