Kryptolebias marmoratus - The Mangrove Killifish
Kryptolebias marmoratus was first described as Rivulus marmoratus in 1880 by Poey, and later as K. marmoratus by Costa. It is a new world fish that inhabits mangrove swamps and estuaries from coastal Florida through Central America to Brazil and the Caribbean Islands. Due to the nature of these habitats, it is highly adaptable and can live and breed in water conditions ranging from fresh water to hypersaline.
Unless you like brownish-grey fish, K. marmoratus is not an attractive fish. Some people would consider it downright ugly. It makes up for that by being interesting, for a number of reasons. Recently scientists have found that it can spend a great deal of time out of water, up to 66 consecutive days. It spends its time in leaf litter, rotting logs, and mud burrows formed by insects or crabs. It was considered rare in much of its US habitat as it wasn't being found in great numbers. Until researches found them by the hundreds in rotting logs. In the aquarium, if your tank is not full and you have something floating on the surface, you'll likely be able to sneak up on them out of the water. Mine spends time on the cork for a spawning mop, and occasionally sticking to the aquarium glass.
K. marmoratus is most famous for being one of only 2 known self fertile hermaphrodite vertebrates. The other is the closely related K. ocellatus. This means that one fish is generally a breeding "pair" and while sexual reproduction takes place, offspring are basically clones of the parent. Males do exist and will sometimes form in aquarium populations. Formation of males can happen for a number of reasons, but typically they form in response to environmental conditions. One way to trigger them is to raise the fish in saline or hypersaline conditions. Males are somewhat more attractive than females, having some yellow in the fins and a light covering of blue iridescence.
I found Kryptolebias marmoratus fairly easy to spawn and raise in a typical mop-spawning killifish type setup. I use a 2.5 gallon aquarium with a sponge filter, spawning mop, and a tight fitting lid. Remember that they're found out of water? They travel by jumping. A lid with only a hole big enough for an airline is important, otherwise they WILL find their way out.
As stated, this fish is adaptable to a wide range of water conditions, but water should be fairly hard. My water is relatively hard out of the tap, and I add some reef salt for this fish. I typically don't measure it out, just grabbing a clump from the bag, but I usually estimate about a tablespoon. I perform 80% water changes every week. Temperature can range from 70 to low 80s for this fish, mine have been breeding fine at 70-72.
K. marmoratus isn't terribly picky about food, but it does need more than just flake food. Mine gets frozen bloodworms, frozen Mysis, live fruit flies, and live redworms regularly. This is occasionally supplemented with repashy and flake. They have a large appetite and can eat quite a lot of food.
Breeding this fish isn't terribly difficult. You have an advantage of having to please only 1 fish here, no incompatible breeding pairs! They lay eggs in plant matter, gravel, or in my case a spawning mop. In the mop eggs are usually found near the top, as tight to the cork as the fish can get them. I pick eggs daily and place them in a dish with chlorinated water, I change water on the eggs every day until I see development. This cuts down on the number of fungused eggs, which I remove as they appear. Eggs hatch in 14-21 days and fry are able to eat newly hatched brine shrimp immediately.
As the eggs hatch, I transfer the fry to a 2.5 gallon aquarium, half filled with aged water and a clump of java moss or najas. I feed baby brine and microworms daily. After the first week I raise the water level a little every day until the tank is full. At the end of week three I start doing 25% water changes. After the fry surpass the 1/4" mark, these water changes are increased in quantity to 80% per week. Fry growth is moderate and juvenile fish should start laying fertile eggs in 6 months or so.
K. marmoratus is most famous for being one of only 2 known self fertile hermaphrodite vertebrates. The other is the closely related K. ocellatus. This means that one fish is generally a breeding "pair" and while sexual reproduction takes place, offspring are basically clones of the parent. Males do exist and will sometimes form in aquarium populations. Formation of males can happen for a number of reasons, but typically they form in response to environmental conditions. One way to trigger them is to raise the fish in saline or hypersaline conditions. Males are somewhat more attractive than females, having some yellow in the fins and a light covering of blue iridescence.
I found Kryptolebias marmoratus fairly easy to spawn and raise in a typical mop-spawning killifish type setup. I use a 2.5 gallon aquarium with a sponge filter, spawning mop, and a tight fitting lid. Remember that they're found out of water? They travel by jumping. A lid with only a hole big enough for an airline is important, otherwise they WILL find their way out.
As stated, this fish is adaptable to a wide range of water conditions, but water should be fairly hard. My water is relatively hard out of the tap, and I add some reef salt for this fish. I typically don't measure it out, just grabbing a clump from the bag, but I usually estimate about a tablespoon. I perform 80% water changes every week. Temperature can range from 70 to low 80s for this fish, mine have been breeding fine at 70-72.
K. marmoratus isn't terribly picky about food, but it does need more than just flake food. Mine gets frozen bloodworms, frozen Mysis, live fruit flies, and live redworms regularly. This is occasionally supplemented with repashy and flake. They have a large appetite and can eat quite a lot of food.
Breeding this fish isn't terribly difficult. You have an advantage of having to please only 1 fish here, no incompatible breeding pairs! They lay eggs in plant matter, gravel, or in my case a spawning mop. In the mop eggs are usually found near the top, as tight to the cork as the fish can get them. I pick eggs daily and place them in a dish with chlorinated water, I change water on the eggs every day until I see development. This cuts down on the number of fungused eggs, which I remove as they appear. Eggs hatch in 14-21 days and fry are able to eat newly hatched brine shrimp immediately.
As the eggs hatch, I transfer the fry to a 2.5 gallon aquarium, half filled with aged water and a clump of java moss or najas. I feed baby brine and microworms daily. After the first week I raise the water level a little every day until the tank is full. At the end of week three I start doing 25% water changes. After the fry surpass the 1/4" mark, these water changes are increased in quantity to 80% per week. Fry growth is moderate and juvenile fish should start laying fertile eggs in 6 months or so.
Greaat blog you have here
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