Article by Jessica Drake
Species: Dimidiochromis compressiceps
Synoma: Haplochromis compressiceps
Common name: Malawi Eye-Biter
Origin: Lake Malawi
Localities/Morphs: Lake-wide distribution, there is a "gold" morph where the females are a gold colour (males are normal colour) but it is thought that this colouration may relate to a particular diet as when this morph is kept in aquarium conditions they revert to the normal silver colour.
Maximum size: 25cm
Natural habitat: Shallow waters near the lake shore (less than 10m depth), particularly amongst Vallisneria beds (a reed-like aquatic plant)
Natural foods/prey: when small (less than 4cm) they eat plankton, when larger they become an ambush predator mainly eating juvenile fish and fry. They hang around in shallow waters and Vallisneria beds because this where other mouthbrooders relaese their fry. Apparently they will adopt a "headstanding position amongst the Val plants when waiting to ambush prey.
Water chemistry in the wild: pH 7.5-9.0, 10-11 dH
Predators: larger fish and other Dimis when they are small, when they are fully grown probably only large birds are likely to eat them
Brood size: very large for a mouthbrooder, can be upwards of 150
Sexual dimorphism: Males have an iridescent sky-blue body, the dorsal fin has red colouring caudally, the anal fin is red and has egg spots. Females are silver with a horizontal black stripe which bisects the body although they can "turn off" the black stripe at times and be completely silver. "Gold" morph - females have a distinctive gold colour to the body and fins.
Breeding method: maternal mouthbrooder
Minimum tank size: Standard 4ft for a small well-behaved colony; in many cases this is probably too small and at least a 4ft x 2ft x 2ft would be minimum. I have bred mine in a standard 4ft (at one time 2 males and 4 females, as they became older and bigger the subdominant male had to be moved) but I was fortunate to have a very non-agressive male.
Sex ratio: 1 male to at least 4 females is best
Tolerance of conspecifics: Can be quite variable - some individuals are relatively placid and tolerate each other well provided they are in a large tank and females have adequate hiding places. Some individuals (particularly males) can be extremely agressive and will kill other males and may seriously injure or kill other females.
Tolerance of heterospecifics: very good with other large species. Will eat any fish that can fit in their mouths as they are predatory in nature.
Water chemistry in aquaria: pH 7.5-9.0, dH above 8
Temperature range: 23-26 is ideal, can tolerate a couple of degrees either side of this
Foods accepted: practically anything, for adults preferably "chunky" food such as pellets rather than flake
Special requirements: none in particular other than water chemistry
- Watch out for deformities when buying fish for breeding purposes - in particular of the head area. A good specimen should have a straight nose as opposed to have a bump on the nose. I have seen some mouth deformities where the corners of the mouth looked like they had been stretched sideways - making the fish look like "The Joker" from the Batman movie!
- In my experience the females can be prone to spitting their eggs very easily (so when catching them to strip then do it as quickly as possible with least stress) particularly when hassled by the male or other females. Give holding females a number of hiding places so they can get away.
- Despite being a mean-looking predatory fish they can be skittish in aquariums. Sometimes giving them Val plants (real or fake; fake ones can be made pretty effectively using strips of green garbage bag tied to a weight - just make sure it can't get into filter intakes) to hide in can make them feel more secure as it mimics their natural habitat. Tight fitting lids for their tank are a must as when spooked they can easily jump out.
- The name "Malawi Eye-Biter" relates to a belief that this fish hunts by attacking and eating the eyes of other fish, however it is now widely accepted that this is actually a rare behaviour for this fish. They prefer to just "gulp" a whole fish down... In some of my fry raising tanks however I have noted that fry kept with Dimi fry tend to end up with a few one-eyed or no-eyed fry, which doesn't happen in tanks where there are no Dimi fry! I have never caught them in the act of eye biting but I have learnt the hard way that even very small Dimi fry have all the predatory instincts at a very early age.....even if only slightly smaller fry are put in with them, if they fit in their mouths the Dimis will eat the other fry, or at least try to.