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Heterandria formosa
Dwarf Livebearer, Least Killifish, Mosquitofish, Dwarf Top Minnow

 Age of Aquariums > Freshwater Fish > Dwarf Livebearer - Heterandria formosa

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Heterandria_formosa_1.jpg (19kb)
Photo Credit: Nonamethefish

Name: Heterandria formosa
Size TankpHTemp
Origin: Southeast USA
3 cm 30 L 7.5 24C


Keeping and breeding Heterandria formosa

Since seeing a picture of this fish in the beginning of my hobby, I was fascinated. Imagine, a fish in which the males are half the size of females, around 1.5 cm max! The females are about 2-3 cm. Of course, I knew these guys were not available to me at that time at the price I could afford. However, around May, I noticed a website offering them at about 1 dollar each. My 40 liter tank received a makeover, and in July the fish had arrived. They spent about 2 days in the mail, but looked just fine when I pulled them from the bag. The 10 fish were netted out and placed in the tank. The tank was planted with some little java ferns which waved loosely in the current, not yet attached to the lava rock. A couple dwarf lily plants had begun producing submerged leaves. This tank was rather bare, and once they were in the tank, they disappeared. The largest male disappeared about a week later. He probably died because of swimbladder disorder which he showed after 2 days in the tank (sinking to the bottom). The remaining 2 males immediately set to work courting the 4 bulky females. It was amusing to watch as they stalked them, turning and twisting to remain directly behind the females, waiting for the right moment. The other four were juveniles. This tank weathered a BGA outbreak a few weeks after the new fish were added. It gradually backed off as the plants began to do better, along with frequent water changes. The ghost shrimp were removed because one was spotted grabbing a juvenile in its pincers. The little fish wriggled free. On the 2nd day in the tank, I spotted a baby about the size of a large baby guppy attempting to get air at the surface. After several tries, the swimbladder filled with air, and the little fish swam to the java ferns to feed. Over the next month, we counted 6. This number stayed stable for a long time, despite new babies. I decided that the babies were dying. So the next feedings were finely crushed flakes sprinked on the surface and swirled into the water to distribute them throughout the tank. This seemed to work well, as the babies, when young, hid in the plants. Only when they grew a bit did they venture out into the open. The largest one, eventually turned out to be a male. Females developed, and as more babies began to survive the number rose.

The tank is densely planted and lit with a 15 watt flourescent bulb. The number of fish right now looks like about 30 or so fish. The fishy receive finely ground flakes swirled into the water and occasional feedings of frozen baby brine shrimp. During the summer, I raised daphnia, and they relished that, along with the cyclops mixed in. Currently there are 3 functioning males, 2 immatures, 7-9 breeder females, and about 20 or so juvies. Needless to say, things are starting to get crowded. Since these fish are small, they take up very little bioload, so this tank is still low maintenance. A couple red ramshorns, limpet snails, and scuds have found their way into the tank. Looking into this tank, you see mainly the juveniles and the males. The females are shyer, hiding around the back and seldom appearing until feeding time.

A little overview about this livebearer: As stated before, the males are very small. Both sexes sport the same "colors". The fish is brown with a horizontal brown black stripe going from the mouth to the tail base. The stripe is intersected by vertical brown black stripes. The amount of striping varies from fish to fish. Some also have blotches in place of stripes on their backs. The small and rounded dorsal fin shows a black spot. On some fish (most of mine) this black spot has a red ring around it, the only bit of color in the fish. The anal fin of females (only) also has this spot. The belly to the gill plates is white. The males are slender, with very long gonopodiums. Just for fun, the gonopodium is twice the size of a guppy's! It usually spans one third the length of the fish. The females are much bulkier. Both sexes are beautifully done creations. This fish is quite shy at first, but later comes out to accept food. They never beg for food, and still dash behind the lava rock when my hand goes over the tank. After I sit back, they come out and begin feasting on the flakes. The babies swim through the cloud, snatching morsels. The adults are quicker at this, but seldom fight over food, other than snatching pieces from each other should both want the same one. However, should lots of food end up in one place, the largest female will sometimes stake a claim and defend it. Fights between males, females, and even juveniles arise occasionally. The stripes and patterns lighten, the gill plates appear to puff out slighty (making the fish look like it's swallowed a mighty mouthful). The fighting fish circle, and sometimes "charge" each other until one retreats. These skirmishes seldom last over a minute, and the longest I've seen is about 10 (interrupted by feeding and losing sight of each other). The male to male fights seem to show who's dominant, but the female ones are pretty odd. The most revved up fish wins, even if it is considerably smaller. Fry are produced by superfoetation, which means that there are eggs of many different stages in the female at one time. This results in babies produced in sets of two or three randomly (rather than batches).

Overall, this fish is an excellent fish to keep. These cute little fish are great for small planted tanks. Try them; you'll like them!

Contributed by Nonamethefish

Another common name for this species is the Lesser Killie Fish. I have successfully kept a school of six individuals in a goldfish bowl. These delightful fish are common in central Florida and are easily collected in shallow waters. Wild caught fish adapt well to aquariums and are not picky on food. If you want to put these fish in a community aquarium, be very careful because they are easily intimidated by faster fish or eaten by bigger fish.

Contributed by Jenny Szilagyi

I was netting minnnows at a local pond he in N. Central Florida and caught a couple of what looks like these, along with the minnows. I have them in a tank where I raise fry in, and have been watching them closely. Since they were so tiny I thought they were babies and didn't want them to suddenly grow and start feasting on my fry. Well, after several months they haven't grown. Now reading this review I realize they may be adults after all. One is about a 8 mm, the other 1.3 cm. They are way too small for me to get a decent pic of them. I think I will set them up differently and see if I actually have a pair and if they produce live young then I will know!

Contributed by Debbie

I had a group of these little guys for a couple years and they were fun to watch! I caught my group in the lake in my area thinking they were minnows. They are also called lesser killifish. Mine were all only about 2.5 cm or a liitle bit less. I kept a large group in a 40 L. They are very easy to breed!

Contributed by Tyler Costolo

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