Feather-Fin Pearl Fish / Featherfin Pearlfish (Simpsonichthys constanciae)

Featherfin Pearlfish care overview

The Feather-Fin Pearl Fish, also written as Featherfin Pearlfish, is a small Brazilian annual killifish supplied here at about 2.5-5 cm. FishBase and Killi.co.uk currently list the species as Simpsonichthys constanciae; the trade name Cynolebias constanciae is the older trade name and some specialist killifish keepers may also know the fish as Ophthalmolebias constanciae. The listing keeps those names together so customers and search engines can connect the same fish without forcing awkward keyword phrases into the copy.

This is a rewarding specialist fish rather than a casual community-tank impulse buy. It comes from temporary freshwater habitats in Brazil, with aquarium references pointing to Sao Joao basin / Rio de Janeiro annual-killifish habitat, soft to neutral water and bottom-spawning behaviour. The beauty of the species is subtle at first: males develop extended dorsal and anal-fin rays with pearly, gold, green and blue highlights that show best under calm lighting over a dark, planted setup.

Quick facts

• Current scientific name: Simpsonichthys constanciae
• Supplier / older name: Cynolebias constanciae
• Common names: Feather-Fin Pearl Fish, Featherfin Pearlfish, Constanciae killifish
• Supplied size: approximately 2.5-5 cm
• Adult size: up to about 6 cm total length
• Temperature: 20-23 C target; keep stable and avoid prolonged overheating
• Water: pH 6.0-7.2, soft to moderate hardness, very clean water
• Setup: covered species aquarium, floating cover, fine sand and a peat or coco-coir spawning pot
• Diet: small frozen and live foods, with quality small prepared foods accepted by settled fish
• Breeding style: South American annual killifish, bottom/diving spawner with eggs incubated in damp substrate
• Delivery promise: packed for licensed live-animal courier service and covered by our Live Arrival Guarantee

Natural habitat and behaviour

Simpsonichthys constanciae is tied to temporary freshwater pools and pond-like habitats in Brazil. In nature, annual killifish live quickly because their pools can dry out; the adults spawn into soft bottom material, while the eggs survive a damp resting period before the next wet season. That life history is exactly why this species should be kept with more intention than a normal community fish. Stable water, a secure lid and low-stress tank mates matter more than a large, busy display.

In the aquarium it is best treated as a quiet species fish. Males display with raised fins and rich speckling, and they can show territorial behaviour around spawning sites, but this is not a rough cichlid-style fish. The safest display is a pair or small group in a covered aquarium with shaded planting, floating plants, leaf litter or wood, and a removable peat or coir container for spawning. Very active barbs, fin nippers, large fish and shrimp that could be eaten are poor choices.

Aquarium setup

A 40 litre or larger covered aquarium is a better retail recommendation than the tiny breeding tubs sometimes used by experienced annual-killifish breeders. Use gentle filtration, an established biological filter and a soft substrate area. Floating plants such as Salvinia, frogbit or water lettuce help break up light, while Java moss, fine-leaved plants and root tangles give females and subdominant fish places to rest. Leave open feeding room at the front so you can check that every fish is eating.

Keep the water cool-stable rather than hot. FishBase gives aquarium conditions around 22 C, while Killi.co.uk breeding reports cluster strongly around 20-23 C with some warmer reports. For a home display, aim for 20-23 C, pH around 6.0-7.2 and soft to moderate hardness. A small weekly water change is safer than large swings, especially for fish that have just arrived. Ammonia and nitrite must stay at zero.

Feeding

Featherfin Pearlfish are micropredators. Offer small frozen or live foods such as cyclops, daphnia, baby brine shrimp, mosquito larvae, finely chopped bloodworm and white worm in modest amounts. Settled fish may take high-quality small granules or crushed freeze-dried foods, but colour, condition and breeding response are best when frozen and live foods form the core of the diet. Feed lightly once or twice a day and remove leftovers because annual-killifish setups are often small and soft-water systems do not forgive pollution.

Compatibility and buyer fit

This fish suits keepers who enjoy specialist behaviour, careful observation and source-backed husbandry. It is peaceful enough for very calm companions of similar size and requirements, but the best result is normally a species setup. Avoid fast danios, robust barbs, aggressive cichlids, large livebearers, fin nippers and small ornamental shrimp. If you want to breed it, keep it species-only and give the fish a dedicated spawning container from the beginning.

The natural lifespan of annual killifish is shorter than many community species, so the value of this fish is not just how long one individual lives. The real pleasure is seeing male display, courtship, feeding response and, for experienced keepers, the annual egg cycle. Buy it if you are happy to keep a covered, quiet aquarium and feed small foods well; choose a hardier community species if you want a low-maintenance mixed tank.

Breeding notes

This is a bottom-spawning annual killifish. Specialist reports describe peat or similar spawning substrate, and the Killies and Splitfins spotlight describes the pair diving into soft mud in nature or peat/coco coir in aquaria. A practical setup is a small pot or tub of boiled, rinsed peat fibre or coco coir deep enough for the fish to push into. Condition adults with live and frozen foods, then remove and inspect the substrate on a schedule that suits your experience level.

FishBase notes a bottom-spawning habit and a four-month incubation reference, while breeder reports vary with temperature and method. For a retail care page it is better to say several months and to treat eggs carefully rather than promise a fixed hatch date. Keep the substrate damp, not wet, and research annual-killifish incubation before attempting to dry or hatch eggs.

What to expect from this listing

The source photo has been added because it gives a real visual reference for SKU 3072. The gallery views are supporting aquarium-scene illustrations, but the source image should be used when judging colour and body shape. Stock is sent through our live-fish packing process with heat or cool control as needed, licensed live-animal courier handling and the Live Arrival Guarantee.

Source notes

Care facts were checked against FishBase for size, temperature, pH, bottom-spawning and aquarium-use notes; Killi.co.uk breeder reports for soft acidic water, 20-23 C breeding reports and peat-style spawning; Killies and Splitfins for diving-spawner behaviour, male colour notes and coir/peat spawning context; and our stock records for supplied size and the trade name printed in the stock list.