Johnstoni OB Care Guide - Aquarium Setup, Diet & Breeding

Johnstoni OB are an orange-blotched form of Placidochromis johnstoni, a Lake Malawi haplochromine cichlid. Their pattern combines irregular orange or rust-coloured markings with the blue, grey or silvery tones associated with the species, although the exact balance varies between individuals and strains.

Placidochromis johnstoni is native to Lake Malawi in East Africa, where it occurs in the lake’s rocky and sandy habitats. The OB form is an aquarium-trade colour variety of this Malawi cichlid rather than a separate naturally occurring species.

A group or harem is best housed in an aquarium of at least 250 litres, with a footprint around 120 x 45 cm; a larger 300-litre aquarium is preferable for a mixed Malawi community. Use fine sand or another smooth substrate, open swimming space and sturdy rockwork forming caves and visual barriers. Moderate water movement, strong filtration and stable, alkaline water are important, while rocks should be placed securely because these cichlids may rearrange the substrate.

Males can reach about 15 cm (6 in) in total length, while females are usually slightly smaller at around 12–13 cm (4.7–5.1 in).

In nature, Placidochromis johnstoni feeds mainly on small invertebrates and other tiny organisms picked from or disturbed within the substrate. Offer a varied carnivorous cichlid diet based on quality sinking pellets or granules, supplemented with frozen or live foods such as brine shrimp, mysis and daphnia. Feed modest portions and avoid fatty mammalian foods; vegetable-based foods can be offered occasionally but should not dominate the diet.

Johnstoni OB can be kept with other reasonably peaceful Lake Malawi haps and peacocks of comparable size, provided the aquarium has ample space and compatible temperaments. Suitable companions may include Copadichromis, Aulonocara and other Placidochromis species, although colour and body-shape overlap can encourage hybridisation. Avoid mixing them with highly aggressive mbuna, very timid fish, small community species or closely related fish when breeding purity matters.

Johnstoni OB are maternal mouthbrooders. Spawning usually takes place over a cleared patch of sand or rock, where the female collects the fertilised eggs into her mouth. She then incubates them for around three weeks, during which time she may eat very little. A separate breeding aquarium or carefully planned rockwork can improve fry survival, as the female and free-swimming young may be harassed by other fish. Newly released fry accept baby brine shrimp and finely powdered fry foods.

Mature males are generally larger and develop stronger blue or metallic colouration, with more intense orange-blotch contrast and longer, more pointed fins. Females are usually smaller and less vividly coloured, although orange-blotched markings may occur in both sexes and can make sexing young fish difficult.