The Checkerboard Cichlid is a miniature South American cichlid from the blackwaters of the Rio Negro, needing very soft acidic water and calm tank mates.
Overview
Dicrossus filamentosus is one of the most elegant dwarf cichlids of South America and at the same time one of the most demanding. The species inhabits the Rio Negro and upper Orinoco basins across Brazil, Colombia and Venezuela, keeping to shallow marginal pools with almost still water, a thick carpet of fallen leaves and submerged branches. By aquarium standards the water in these biotopes is extreme: clear but dark brown with tannins, with hardness close to zero and pH dropping to 4.5-5.0.
Males reach 7 cm excluding the fins and are easily recognised by the lyre-shaped tail with two long filamentous rays — the source of the specific epithet filamentosus. A double row of dark square blotches runs along the midline, forming the characteristic checkerboard pattern. Females are noticeably smaller (around 5 cm) with a rounded tail, but they transform in spawning dress: the belly floods crimson and a black field appears in the dorsal fin. Lifespan is 4-6 years.
In temperament D. filamentosus is peaceful and even timid — not a territorial aggressor but a cautious fish that, under bright light and among boisterous neighbours, simply hides and refuses food. Care level is intermediate and is dictated entirely by water chemistry: in hard tap water the species does not live long and will not breed at all.
Related dwarf cichlids with simpler requirements are the Ram Cichlid and Agassiz's Dwarf Cichlid; beginners are better off starting there.
Tank Requirements
The minimum for a pair is 60 litres; for a group of one male and two or three females, 100 litres and upwards at 80 cm long. Height is irrelevant — the fish keeps to the lower third of the tank.
Water parameters: temperature 24-28 °C, pH 4.5-6.5, general hardness (GH) 2-8 dGH. In practice aim at the lower part of that range — pH 5.0-6.0 and GH 2-4 dGH. That almost always means RO-based water; ordinary tap water will not do. A low pH is nothing to fear, but below 2 dGH the buffering capacity disappears and the reading can crash overnight, so monitor it regularly.
The layout recreates a flooded forest biotope: fine dark sand, driftwood, branches and, crucially, a thick layer of dried almond, oak or beech leaves. The litter is not decoration but a functional element — it acidifies the water, releases tannins and hosts the microfauna the fish pick at between feedings. Keep the lighting dim, ideally diffused by floating plants.
Flow should be minimal. An air-driven sponge filter or an external filter with the spray bar aimed at the glass works best. Plants are welcome, but few survive in soft acidic water — cryptocorynes, microsorum and java moss on driftwood are the reliable choices.
Feeding and Diet
In nature D. filamentosus picks small crustaceans, insect larvae and other microfauna out of the leaf litter. It is a pronounced micropredator with an awkward relationship to dry food: many specimens, wild-caught ones especially, ignore it entirely at first.
The diet should be built on live and frozen foods of the right size: brine shrimp and their nauplii, cyclops, daphnia, small bloodworms, microworms and grindal worms. Introduce dry food — quality micro-pellets for dwarf cichlids — as a supplement, training the fish onto it gradually and without expecting it to replace live food.
Feed two to three times a day in small portions. Make sure the food actually reaches the bottom: Checkerboard Cichlids are slow feeders and easily go hungry if quick characins share the tank. Remove what is not eaten — in soft, poorly buffered water, organics shift the parameters especially fast.
Care and Maintenance
Change 20-30% of the water weekly, always with pre-conditioned water of the same composition. Stability matters more here than the absolute figures: the species reacts far more painfully to a jump in hardness or pH than to the value itself.
Keep pH and GH test kits to hand and check at least weekly — in weakly mineralised water the parameters drift imperceptibly. Ammonia and nitrite should read zero, nitrate below 20 mg/l. Rinse the filter in old tank water every three to four weeks.
Refresh the leaf litter as it breaks down, removing fully disintegrated leaves and adding new ones roughly once a month. There is no need to strip it out completely — the biofilm that develops on it feeds both adults and fry.
A healthy Dicrossus hovers calmly above the bottom, holds its fins spread and forages actively in the litter. Warning signs are a fading checkerboard pattern, clamped fins, breathing at the surface and refusing food. The species is prone to ich and to bacterial infections when parameters are unstable; quarantine new arrivals for at least three weeks, since weakened wild-caught fish are common in the trade.
Compatibility
D. filamentosus is harmless to everything and belongs in a peaceful South American biotope tank. The main task is not to add anyone who will intercept its food or frighten it.
Good companions are small, calm characins and bottom dwellers that share the soft acidic water requirement: Green Neon Tetra, Ember Tetra, Dwarf Pencilfish, Pygmy Corydoras and Otocinclus. Among dwarf cichlids, Borelli's Dwarf Cichlid works if the tank is long enough for the territories not to overlap.
Unsuitable: large and boisterous species, the Tiger Barb and active danios included — they will leave the Dicrossus hungry; any medium or large cichlid; and every species needing hard alkaline water, whose requirements simply cannot be reconciled with this biotope.
Shrimp are a workable combination: the fish leaves adult neocaridina alone, though it will take small shrimplets given the chance.
Breeding
Breeding D. filamentosus is a job for an experienced aquarist, and it comes down to a single parameter. The egg membrane only functions properly in very soft water: above 2-3 dGH the overwhelming majority of eggs fail to fertilise. Target conditions are GH 0-2 dGH, conductivity below 50 µS/cm, pH 4.5-5.5 and a temperature of 28 °C.
Unlike most dwarf cichlids, Dicrossus do not hide the clutch in a cave. They are open substrate spawners: the female chooses a leaf, a flat stone or a patch of driftwood, cleans it thoroughly and lays 50-150 eggs.
The family structure here is maternal. The female guards and fans the clutch alone and then shepherds the fry, while the male patrols a larger territory and takes almost no part in raising them. The species is polygamous in the wild, and in a spacious tank one male serves two or three females — this makes spawning easier to obtain and reduces the risk of him harassing a single partner.
Incubation takes about three days, and the larvae then lie on the substrate for another four or five. Free-swimming fry are fed infusoria and rotifers, moving on to brine shrimp nauplii and microworms from a week old. Growth is slow, and that is normal: the checkerboard pattern appears at two to three months, and the filamentous tail rays on males not before six. Keep water changes in the grow-out tank small and daily, using strictly the same water as in the breeding tank.