Demasoni

Quick facts

Adult size

8 cm

Lifespan

can live up to 10 years

Tank zone

middle

Temperament

aggressive

Difficulty

intermediate

Water parameters

Temperature

24–28°C

pH

7.5 to 8.8

Hardness

10 to 25 dGH

Tank requirements

Minimum volume

250 L

Minimum length

120 cm

Flow

moderate

Lighting

moderate

Substrate

sand

Hiding spots

needed

Open swimming room

needed

Feeding

Diet: herbivore, feeds primarily at the middle.

Herbivore. Spirulina-based flake and pellets should make up the majority of the diet. Blanched peas, blanched spinach, blanched zucchini, and nori seaweed are supplemental greens. Frozen brine shrimp and mysis shrimp can be offered occasionally but avoid making high-protein food a staple. Bloodworm is especially risky for Mbuna; the link to Malawi bloat isn't proven but the association is strong enough that most experienced keepers avoid it. Feed small amounts 2-3 times daily rather than one large feeding.

Vegetable matter required (algae wafers, blanched zucchini, spinach).

Compatibility

• One of the most aggressive Mbuna relative to its size. Demasoni are small (7–8 cm) but pack the attitude of a fish twice their size. Males in particular are relentless territory defenders and will kill subdominant males if the tank is too small.
• The standard Mbuna overstocking strategy is critical for demasoni. Keep a group of 12+ with a ratio of 1 male to 4-5 females. This spreads aggression across many targets rather than concentrating it on one or two victims. In groups under 8, the dominant male kills off rivals one by one.
• Tankmates should be other Mbuna of similar size and temperament. Avoid larger or much more aggressive species that will dominate them, and avoid much smaller or more peaceful fish that will be terrorized.
• Don't keep with other blue-and-black-barred Mbuna (Pseudotropheus saulosi, P. demasoni look-alikes). Similar color patterns trigger the strongest inter-species aggression in Mbuna.

Habitat

Endemic to Lake Malawi, found specifically around Pombo Rocks in Tanzanian waters and nearby rocky shorelines. Wild populations occupy a very restricted geographic range. The rocky littoral habitat provides the crevices and caves that demasoni use for territory and breeding. The coloring is striking: alternating vertical bars of dark blue-black and lighter blue across the entire body. Males and females look nearly identical in color, which is unusual for Mbuna and makes sexing very difficult. Adults are small for a Mbuna at 7–8 cm, which tempts keepers into understocking, but the aggression level demands the same overstocking approach used for larger species. The species was first described in 1994 by Konings and named after Laif DeMason, a prominent cichlid collector and dealer. It quickly became popular in the hobby due to the intense coloring and became widely bred. Tank-bred fish are the standard; wild-caught are rare in the general trade.

Breeding

Maternal mouthbrooder, standard Mbuna reproduction. The dominant male displays on a flat rock. The female deposits eggs, picks them up in her mouth, and is stimulated to take in sperm by the male's anal fin egg spots. The female incubates 5-15 eggs for 18-21 days without eating. Fry are released at about 8–10 mm and eat crushed spirulina flake from day one. In a community Mbuna tank with rock cover, some fry survive. For maximum survival, strip the female at 14-18 days or let her release into a breeder box. The small clutch size and slow growth rate compared to larger Mbuna means colony expansion is slower. Demasoni breed continuously in well-maintained tanks.

Common problems

Aggression-related deaths are the primary concern. The single most important factor in keeping demasoni alive is group size. In groups under 10 in a standard 200-liter tank, one male will systematically eliminate rivals until only he and a handful of females remain. Groups of 12-15 with extensive rock piling to break sightlines are the minimum. Malawi bloat affects demasoni the same as other Mbuna: swollen belly, stringy white feces, lethargy, rapid breathing. Caused by dietary issues (too much protein, not enough fiber) and stress. Treat with metronidazole early; bloat progresses fast and is often fatal by the time symptoms are obvious. The identical coloring of males and females makes it impossible to buy a specific sex ratio at the store; you're guessing. Buy 12+ juveniles and let them sort themselves out.

Bioload

Bioload coefficient: 3.0 (8 cm mbuna, moderate waste but kept in large groups).

Bioload coefficients are calibrated against the neon tetra as the anchor (1.0). See the methodology page for the formula and how each value was derived.

Further reading

• How to cycle a fish tank
• Stocking ideas by tank size