Fish, Tanks and Ponds


Fish, Tanks and Ponds
A comprehensive guide to fish

Pseudotropheus demasoni

Pseudotropheus demasoniPseudotropheus demasoni
Photos by Andy Rapson

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 average dGH is 7 - 9
  • The average pH is 7.8 - 8.5
  • The average temperature varies throughout the year from 23 - 28°C

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.

Etymology:

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

General Notes:

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.
They seem less aggressive with other species than with their own. Most other mbuna will probably be ignored.

Feeding

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.
Use some fresh greens such as nori, blanched spinach, sliced cucumber and lettuce. A good quality spirulina flake should be used to supplement this to ensure a balanced diet

Sexing

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.

Breeding

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.
After spawning has taken place leave the fish as they are for a few days in order to allow the female to bond with the eggs or she may spit them out if caught to soon, but don't leave it to long because there is a chance that the fry may be harmed in the transfer if they have hatched, two to three days is about right to make the transfer. Don't offer any food to the brooding mother because she won't eat while brooding.

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.

Wild status

Due to their very small natural range the IUCN Red List of Endangered Species list P. demasoni as being vulnerable.

Additional information

Due to their extreme aggression only keep this fish with other very robust mbuna and not with any of the more passive species.

Information at a glance

H: 7.6 - 8.4
dGH: 7.8 - 8.5
Temperature: 23 - 28°C (74 - 82°F)
Lighting:
Diet: Herbivore
Size: 6.3cm (2.5in)
Min tank size: 225 litres
Difficulty level: Difficult
Aquarium type: Mbuna community
Swimming level: All levels

Distribution and habitat

distribution map for Pseudotropheus demasoni

Origin: E Africa. Endemic to Pombo Rocks, Lake Malawi, Tanzania

Habitat: Rocky reefs in shallow water.

Classification

Kingdom: Animalia
Phylum: Chordata
Class: Actinopterygii
Order: Perciformes
Family: Cichlidae
Genus: Pseudotropheus
Species: P. demasoni Konings, 1994

Other common names:
None

Synonyms: None