Osteogaster eques

Osteogaster eques is a fun and fascinating fish to keep, but it is somewhat more challenging to breed, which can be a nice challenge.

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Osteogaster eques

Osteogaster eques was first described in 1877 by the Austrian fish lover Franz Steindachner. At that time still with the name Osteogaster eques. They belong to the family Callichthyidae or the Armored Catfish. They got this name because of the possession of 2 rows of bony plates on the flank of these fish. They do not have scales but a kind of armor. It is a fairly large family with about 300 species, but some have not yet been described.

The genus name Osteogaster can be broken down into two Greek words: ostéon (Gr. ὀστέον), bone; gastḗr (Gr. γαστήρ), belly, referring to the coracoid bones of O. eques, which, unlike those of Gastrodermus elegans, enclose the abdominal region. The species name eques is from Latin and means Knight, Horseman or Rider.

Description

The color of Corydoras eques partially depends on the substrate they live on. Their flanks can be fairly dark to a somewhat lighter turquoise/blue. Just behind the eye across their gill plate, they have an orange vertical band. You can find this orange also on top of their back and at the edges of their caudal fin. Sometimes they show a dark band that starts at the top of their head and runs to the back to the base of their caudal fin. The belly is whitish.

With a total length of about 6 centimeters, the Osteogaster eques is average compared to other Osteogaster species. The male remains slightly smaller and can reach a total length of about 5 centimeters. The snout is relatively short. The difference between males and females can be seen in the Corydoras eques once they are adults. The female becomes somewhat larger and is somewhat coarser and rounder built. The male remains somewhat slimmer in shape.

Like all other Osteogaster species, the Osteogaster eques is a peaceful fish. They are somewhat more active than many other species. It will be noticeable that they swim back and forth endlessly, certainly when the school is large enough or when you keep them with only conspecifics in a breeding aquarium. When you come closer to the aquarium, they will also come forward and swim up and down against the glass. It is a school-forming species that feels most at ease in larger groups. Keep them with at least 6 conspecifics, but preferably many more.

You can keep them in a community aquarium together with other smaller or middle-sized fish like Tetra’s, Danios or Rasboras. Keep in mind that holding them together with larger fish will make them skittish and hide a lot. If you keep them with fish that will try to eat them they have a nasty surprise. They can spread their pectoral fins and lock them in place, this way they will get stuck in the throat of their predator. It is better not to combine them with bigger, hunting species…you will probably lose both.

Biotope

Their type locality is Rio Solimoes in the Amazon basin near Codajas in Brazil. This town lies halfway between Tefe and Manaus. Not much is known of other locations they could live but from time to time similar-looking fish are being exported from Peru. It is still unclear whether these fish are the same species or not.

Diet

Osteogaster eques forages for its food on the bottom. They are true omnivores; they will eat anything edible. You can feed them with most sinking food, such as live and frozen food such as mosquito larvae, water fleas, tubifex, etc. Flake food, tablets, and granules are also eaten. Keep in mind that their mouths are pretty small.

If you keep them in a community tank, make sure enough food reaches the bottom. Check on them to see if they get enough down there to feed on. Don’t assume they can live on the litter on the ground because the don’t, Corydoras eques don’t feed on detritus (neither does any other Corydoras species).

The Aquarium

Because you have to keep the Osteogaster eques in a school and they dig on the bottom in search of food, you need an aquarium of at least 90 centimeters in length. Set up the aquarium with (filter) sand on the bottom. Fine gravel is often seen in photos, but this is actually not recommended. The Osteogaster searches the substrate for food particles with its barbels. Sharp gravel can damage the barbels. Due to the damage, infections can cause them to lose their barbels completely. So it is better to use sand. I usually use filter sand myself because these sand grains all have the same dimensions, this ensures that the sand does not silt up and can rot.

The rest of the decoration is up to you as long as you provide some cover for the Corydoras eques. You can use driftwood or plants or any other cover you can create.

They will need crisp clean and well-oxygenated water. Make sure to clean your tank very regularly and create some current at the surface. Don’t hesitate to change your water with cooler water, they really love it and you will see them react to the cooler water right away.

Breeding aquarium and conditioning

Breeding Osteogaster eques can pose a more significant challenge than other Osteogaster species. To get better results, you can set up a special breeding tank. Use a smaller aquarium of around 50 centimeters in length. Setup a sponge filter, heating etc. Decorate the aquarium with a thin layer of sand, lots of fine-leaved plants, and some floating plants.

Keep the water parameters stable for a couple of weeks. Feed the full-grown fish with a variety of foods but make sure you also give them black mosquito larvae. Make sure the fish are fully grown and use a ratio of 2 males to every female.

The Spawn

As soon as you see that the females of the Osteogaster eques are nice and full and round, they are full of eggs. You can induce the spawning of Osteogaster by changing about 50% to 70% of the water with cooler water. Provide more aeration by adding an air stone, for example, and give them a bit more current by adding a flow pump. Direct the outflow of this pump at the glass; many Osteogaster species deposit their eggs where the current hits the glass. The Osteogaster eques is sometimes a bit different regarding depositing eggs. These are often deposited between the fine-leaved plants or if there are floating plants near the water surface. It sometimes takes some searching to find what works best for your fish.

Raising the fry

The eggs hatch after 3 to 4 days. They will use up their yolk sack in the next couple of days. As soon as it’s gone, you can start feeding them microworms and newly hatched brine shrimp. As they grow, you can start feeding them larger foods like crushed flakes, etc.

Osteogaster eques fry are highly sensitive to fluctuation in your water quality, so make sure to keep your tank impeccably clean and aerate it. They have a better chance of surviving if you add a thin layer of sand on the bottom instead of using a bare bottom.

The fry are fast-growing. After 10 days they already have a nice colour pattern. Within 5 to 6 weeks they are small copies of their parents. At the age of around 3 months, they are big enough to be moved to a community tank. This attractive Osteogaster is always in demand. Because they are not often offered at stores usually you can sell them at a good price.

Conclusion

You will not often find Osteogaster eques in your local fish shop. If they offer them they will more often be nicely colored Corydoras aeneus so pay attention to what you are buying. Osteogaster aeneus is usually much cheaper than Osteogaster eques. It is a nicely colored and fascinating fish to keep, but a bit harder to breed (which of course again is a nice challenge).

Video

Author

John de Lange

Copyright images

Hung-You Chen
Gert Jan van Beek

Resources

Fcas.wordpress.com
Fishbase.org
Scotcat.com
SeriouslyFish.com

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Additional information

Family

Genus

Species

eques

Synonym

Corydoras eques – Horsemens Cory

Group

First described by

Franz Steindachner

Character

Social behaviour

Breeding behaviour

Diet

Min. aquarium length in cm

90

Zone

Origin

Country

ecosystem

Minimum length

4

Length maximum

6

Temperature minimum

20

Temperature maximum

26

pH minimum

6.0

pH maximum

8.0

GH minimum

2

GH max

16