Featherfin Pearl Killifish (Simpsonichthys constancia) Pair

Common Name

Featherfin Pearlfish, Featherfin Killifish.

Origin and Habitat

This is a Brazilian annual killifish from the coastal plains around the lower Rio São João basin in Rio de Janeiro state. In the wild it inhabits temporary pools, including shallow seasonal waterholes and rain filled pools that appear during wet periods and disappear when conditions dry.

Because this species is reported as critically endangered and has experienced significant habitat loss, captive bred fish are strongly preferred whenever possible.

Biotope

This is a seasonal pool fish. Think shallow water, soft muddy bottoms, and marginal cover during the wet season, with big changes across the year. In an aquarium you can capture the look while keeping maintenance simple and breeding friendly.

Biotope inspired setup basics

• Shallow footprint tank with a secure lid
• Dark sand, or fine soil capped with sand
• Leaf litter and small branches for cover and micro life
• A spawning substrate tray with peat or coconut coir if you want eggs

Biotope fish list, common choices

• Best option is a species only setup, one male with two to three females
• If you add tankmates, keep it to very calm, very small fish in a larger tank, and only if you are not trying to breed

Biotope plants, common and aquarium friendly stand ins

• Java moss for fry cover and micro foods
• Floating plants for cover and comfort
• Dwarf sag or similar runners for margin vibes

Temperature and Water Conditions

Annual killifish care rewards stability. FishBase lists aquarium conditions around 22°C, which is about 72°F, with neutral pH and moderate hardness in their summary. Many keepers run a small range around that value as long as it stays steady and the tank stays clean.

Tropical Fish Co. advice: we do not recommend chasing pH unless you are trying to improve hatch rates. With annual killifish, consistency, clean water, and good food are what move the needle.

Appearance and Size

This fish looks delicate, but it has strong personality. FishBase lists a maximum total length of about 6 cm, which is about 2.4 inches. A detailed taxonomic treatment reports the largest examined specimen at 41.5 mm standard length, which is about 1.6 inches, so most adults feel small even when fully mature.

Male vs female differences

• Males have long, pointed dorsal and anal fins with filament like extensions that can reach past the tail edge. They show four horizontal rows of round black spots along the sides, plus pale blue spotting and light edging on the fins.
• Females have shorter, rounder fins without long filaments. Their body pattern is more barred, often with one or two darker flank spots and pale blue vertical lines.

Diet in the Wild

Like other annual killifish, they are micro predators that pick at tiny aquatic invertebrates and insect larvae in shallow water.

Feeding in Captivity

For best color and breeding, lean into small live and frozen foods. Baby brine shrimp, daphnia, cyclops, and mosquito larva style foods are perfect. High quality micro pellets can be used as a backup once they recognize prepared food. Two or three small feedings per day usually beats one big meal.

Behavior and Tank Setup

They are generally peaceful, but males can posture and spar, especially in tight quarters. A small harem setup often works well. Provide cover so females can take breaks, and keep the lid tight because killifish jump.

If you want to breed, keep the setup simple. A bare bottom tank with leaf litter, a spawning tray, and a seasoned sponge filter is a classic approach that is easy to maintain and easy to harvest eggs from.

Breeding

This is a substrate spawning annual killifish. Adults deposit eggs into fine substrate, commonly peat moss or coconut coir in hobby breeding. Many breeders collect the substrate, store eggs in slightly damp medium, then rewet once embryos are fully developed.

FishBase lists an incubation period of about 4 months for this species. Timing can vary with temperature and how the eggs are stored. When eggs are fully developed, hatching can occur quickly after wetting, sometimes within about a day in common annual killifish methods.

For rearing fry, use shallow water with gentle aeration and a seasoned sponge filter. Start feeding quickly once fry are up and moving. Baby brine shrimp is the workhorse food for most annual fry once they can take it, and clean water is what turns small fry into big fry.

Breeder’s Tips

• Use peat or coir in a tray, it makes egg collection simple
• Condition adults heavily on live foods for two weeks before collecting eggs
• Keep the egg medium damp, not wet, during incubation
• Label bags or tubs with species and date, incubation timing matters
• When you rewet, use shallow water and gentle aeration, and be ready for fast hatches
• Sort fry by size if needed, because bigger fry can outcompete smaller ones

Quick Facts

• Scientific name: Simpsonichthys constanciae, also listed as Ophthalmolebias constanciae in modern references
• Common name: Featherfin Pearlfish, Featherfin Killifish
• Adult size: up to about 2.4 in total length, which is about 6 cm, most adults are smaller in practice
• Temperature: around 72°F, which is about 22°C, a stable small range around this value is commonly used
• Water: around neutral pH with moderate hardness is listed in general summaries, stability and cleanliness matter most
• Temperament: generally peaceful, males posture and spar, best kept as one male with multiple females
• Tank size: 10 gallons, which is about 38 L, works for a breeding trio, larger is better for display groups
• Tank setup: tight lid, gentle filtration, cover for females, spawning tray with peat or coir if breeding
• Diet: micro predator, does best on small live and frozen foods, prepared foods can be trained as a supplement
• Breeding type: annual killifish, eggs are deposited into substrate and incubated in damp medium
• Incubation: about 4 months is listed by FishBase, timing varies with conditions
• Fry foods: baby brine shrimp is the primary growth driver once fry can take it, clean water and frequent small feeds help
• Best for: hobbyists who want a rewarding breeding project and do not mind learning annual egg incubation basics

Tropical Fish Co. Notes

This is a small fish with big style. The males look like they decided normal fins were boring and upgraded to feathered ribbons. If you want a fish that rewards you for learning a new skill, annual killifish breeding is exactly that.