A little about Lake Malawi
Lake Malawi is often quoted as containing hard alkaline water. This isn't so, the water in Lake Malawi is relatively soft when compared with other large lakes in the African Rift Valley.
The difference in pH is accounted for by differing levels of CO2 found in the water. Deeper water and sheltered bays may have higher levels of CO2 and so the pH will be lower. Wind swept shallow water will have a better gas transfer at the surface and so will contain less CO2 making the pH higher.
Lake Malawi contains approx only one third of of the dissolved mineral level of nearby Lake Tanganyika and so chemically the two lakes are very different and this is one reason why it is a bad idea to keep fish from the two different lakes in one aquarium.
Pseudotropheus: Greek, pseudes = false + Greek, tropaion = defeat, a memorial of a fighting war, trophy; because of their specialized teeth were such an obvious feeding adaptation
Despite the relatively small size of P. demasoni
and despite the fact that this species lives peacefully in the wild, in
the aquarium it is one of the most aggressive of all mbuna. It is also one of the most beautiful with its intensely blue stripes. Non-breeding fish are very aggressive with each other. The only way to succeed with this species is to keep a large group so their aggression is diluted over the entire group rather than being concentrated on to one or two individuals. Keep at least ten preferably unrelated fish in the group with just one male although more would be better and keep them in a tank of at least 225 litres. Or they will literally kill each other.
Wild fish feed on what is called aufwuchs which is a German word for the algae and the small invertebrates which live on and amongst it. In captivity it is important that their diet is kept low protein and high fibre or the fish may suffer from a condition known as Malawi bloat which is often fatal.
Males are larger and more intensely coloured when adult and adult males have egg spots on their anal fin, these are either very few or completely absent on adult females. Immature and submissive males could easily be mistaken for females.
P. demasoni is a mouth brooder, the male will select a small territory and prepare it and then begin displaying to any passing female. If the female is ready to spawn she will follow the male to his territory and the pair will begin to circle each other. The eggs are laid and fertilised as the pair circle and then the female will break away and pick up the eggs in her mouth where they are stored in a special brood pouch. The female will then return to the male and the process repeated until all the eggs have been laid. The female will then seek out a quite spot and keep a low profile for the next month until the fry are ready to be released. If left to her own devices one or two fry may grow up to adulthood even in a mbuna community but if you want to raise a brood then the female will need to have a tank of her own.
Some breeders insist on trying to extract the eggs from the female and raise them artificially, this risks injuring the female and there really is no advantage to raising the eggs this way, female Mbuna have been making a great job of it for thousands of years so it is best just to let them get on with it.
Once the fry are released they are fully independent and quite advanced for fry due to their good start in life. Broods are quite small with about a dozen fry being average for P. demasoni.
Try to avoid inbreeding, don't buy all your stock from a single breeder because if you do you will be breeding closely related fish with each other and then the next person will come along and buy all of his stock off you which very quickly over just a few generations lead to inbreeding problems.
Due to their very small natural range the IUCN Red List of Endangered Species list P. demasoni as being vulnerable.
Due to their extreme aggression only keep this fish with other very robust mbuna and not with any of the more passive species.
H: 7.6 - 8.4
dGH: 7.8 - 8.5
Temperature: 23 - 28°C (74 - 82°F)
Size: 6.3cm (2.5in)
Min tank size: 225 litres
Difficulty level: Difficult
Aquarium type: Mbuna community
Swimming level: All levels
Origin: E Africa. Endemic to Pombo Rocks, Lake Malawi, Tanzania
Habitat: Rocky reefs in shallow water.
Species: P. demasoni Konings, 1994
Other common names: