Spectrolebias Costai



Spectrolebias Costai, also known as Cynolebias Costai is named after Mr. Luis Costa as he first discovered Spectrolebias Costai in April 1982. It is generally found in South America and Araguaia Basin, Central Brazil.
It is an annual killifish species popular in the aquarium hobby with its coloration and interesting behavioral characteristics.



Spectrolebias Costai is a blue and black colored, impressively beautiful fish. The males have blue dots on the anal and dorsal fins. The dots are in the form of a single row at the base of each fin. The number of dots varies according to the locations where the fish are collected. Characteristically while the males are impressively colorful, the females are plainer in color with some black to dark brown dots over them. Generally, specimens are 1,8-2,0 cm in length but, they can reach up to 4,0 cm in length.

Behavior and Compatibility


Most of the other killifish species it is also aggressive to females. Therefore, providing hiding places for the females is significant. Keeping this fish in a species-only aquarium is the best option for keeping and breeding. Oak leaves, catappa leaves for decoration, and providing hiding places are suitable to mimic their natural habitat. In nature, during the summer, ponds will dry out, adults will die off, and the eggs will remain in the wet peat until the next rainy season. The fry reaches adulthood in 10-12 weeks and produces the first eggs if adequately fed.

Water Parameters

Water pH range: 6.0 – 6.8.
Temperature: 21 – 29°C.

Proper Tank Conditions

The tank water needs to be slightly acidic and soft. Assuring some hiding places for the females and non-dominant males is necessary to keep the fish properly. Long-lasting (slowly degrading) leaves such as oak and catappa are suitable to create hiding places. Also, decoration with live plants, driftwoods, ceramic caves will improve visuality.
Spectrolebias Costai needs to be kept in a species-only tank for breeding. If there is no breeding interest, they can live together with other non-aggressive and similar-sized fish in a community tank.


Spectrolebias Costai is a Carnivor species. In nature, it feeds on small insects, insect larvae, small crustaceans, and worms. While keeping them in the aquarium, live or frozen foods such as baby brine shrimp (artemia nauplii), water fleas (daphnia), microworms, mosquito larvae, blood worms, tubifex worms, grindal, and white worms are suitable for feeding. Also, they eat high-quality protein-based granule or flake foods.


Spectrolebias Costai is very difficult to breed under aquarium conditions and it is particularly challenging to maintain it over a long period. They require special care to mimic the natural seasonal conditions of their natural habitat. Since they are annual fishes, it is also not sustainable to keep the population for a long time without continuous breeding efforts.

Spectrolebias Costai spawns annually in a way like most annual species. They dive completely into the substratum/peat and spawn there.

In Aquariums, the best method for breeding is to fill a glass or a small jar with peat moss as the spawning container. That will allow easy collection of the eggs. Also, it will help to keep the peat moss in the jar and maintaining the water quality high. The proper depth of the peat should be at least equal to the length of the fish.

After spawning, the spawning container with peat moss should be taken out for incubation. So, it is better to take out and replace the spawning container every 15 days. The peat with eggs must be squeezed in a fine mesh net to remove the excess water until it will get slightly damp. Then the eggs can be stored with peat moss in a plastic zip bag for incubation at 23-28°C. This will imitate the natural life cycle of the fish during the dry season. The incubation period is dependent on the temperature. It will take around 5 months at 23°C and less in higher temperatures.

During the incubation period, the eggs and moisture of the peat must be checked regularly (Every 15 days). Eggs with fungus must be removed immediately from the package to prevent other eggs from getting infected with fungus.
The readiness for hatching can be noticed during regular checks. When the fry got ready to hatch, the eyes will be visible and the fry will be moving in the eggs. For hatching the eggs, the water temperature must be set to 2-3°C less than the incubation temperature before adding the eggs with peat moss into the hatching tank. After putting the eggs in the hatching tank, the eggs start hatching in 1 day. The hatching of the eggs may continue for up to 3 days.

The fry of this species is very small. The fry needs infusoria like ciliate protozoans, paramecia during the first week of their life. Then, gradually micro worms and newly hatched brine shrimps will be suitable for feeding the fry. Water should be partially changed every week to keep the water quality optimal for raising the fry.

After the fry reaches a size that they can eat baby brine shrimp, a larger tank will be more suitable for the fry to grow. While transferring them to a larger tank, first transfer the fry and water to the new tank. Tray to keep the peat remained in the hatching tank. Later, add more water with the maximum volume of the hatching tank water. Also, make sure the new water parameters are like the old tank’s water. A small sponge filter with moderate aeration is also suitable for this stage of growing the fry.

Image Source:
Photos by Rudolf Pohlmann

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