|
|
|
Breeding the Blockheads - Steatocranus casuarius Poll, 1939 and Steatocranus tinanti Poll, 1939. The West African cichlid genus Steatocranus Boulenger, 1899 belongs to the subfamily Pseudocrenilabrinae and is part of the Tilapiini tribe. This may be a surprise to some readers but all members of the Steatocranus genus carry the famous Tilapia spot either as juveniles or throughout their lives. The common name ‘Blockhead’ refers to the well developed fleshy nuchal hump of mature males. All members of this genus are rheophilic (a preference for fast flowing regions of the river such as rapids) and they are well adapted to their environment. Their bodies are typical of rheophilic species in that they are elongated and stream-lined. They also posses a swim bladder that is reduced in size (to varying degrees depending on the species) making it easier for them to maintain close contact with the substrate. They will often sit on the substrate or perch on a vantage point in the aquarium, resting on their pelvic fins and then “hopping” from place to place, a behaviour which makes them reminiscent of the marine family of Gobies. It is easy to distinguish the sexes in adults as males are larger than the females, the males dorsal and anal fins are elongated and mature males posses a well developed nuchal hump.  Steatocranus casuarius and S. tinanti are both found in the Congo River drainage and often in the same locations (the Malebo Pool, Brazzaville and lower regions of the Congo River), although S. tinanti appears to prefer faster flowing stretches of the river. The males of both species will reach up to 6 inches (15cm) Standard Length and the females will reach about 4 inches (10cm) SL in size, although breeding in captivity often happens at a much smaller size. In my experience, if given the correct conditions these fish will easily attain their maximum size and a fully grown mature male is quite an awesome sight!  I have been keeping and breeding S. casuarius since the late 1990’s and I have always found them an easy species to work worth. They are not too fussy about pH or Hardness, as long as it is not too extreme. A neutral or slightly acid pH and soft water are ideal for maintenance and breeding, however I’ve known people maintain them successfully with cichlids from Lake Malawi in hard and alkali water. The most important factor for maintaining any of the Steatocranus are the high levels of dissolved oxygen required in the water, as they can seen gasping at the water surface if the levels of dissolved oxygen in the water are too low. Aiming one or two powerheads across the surface of the water is sufficient to maintain the necessary high levels of dissolved oxygen, though it is not necessary to generate a Jacuzzi in the tank! The fish will naturally avoid the fast moving water and stick to the calmer parts of the tank. I prefer to keep them as a separate species tank with a few target fish such as Congo tetras (Phenacogrammus interruptus), or mix them with other West African cichlids such as Pelvicachromis. Tank decor includes large pebbles, bogwood and earthenware pots for caves. For planting I usually add Anubias and Java fern (Microsorum pteropus). Pairs form readily and remain stable with very little aggression, either between the pair or towards other fishes. Naturally, the spawning cave is well guarded, but tank-mates are not sought out and molested to death, as with certain other cichlids. As cichlids go, S. casuarius has come to mean more to me than most. When I first tentatively introduced my then girlfriend to my bizarre hobby, she was fascinated and started to study my literature collection. After flicking through a Baensch Atlas she insisted that I acquired some blockheads, because they were “cute”! The fish were found and six short years later, without my knowledge, a pair of Blockheads were depicted on the side of our wedding cake! Breeding Blockheads is an exercise in patience. As with most cichlids it is best to buy a small group of juveniles and allow them to form pair bonds naturally (I prefer if possible to buy from more than one source to avoid in-breeding). My current group of S. casuarius consist of the young from a previous generation of my own fish and a handful of juveniles from the British Cichlid Association (BCA) auction last October. I tend to then forget about them until it is possible to distinguish the sexes and typical cichlid courting behaviour can be observed. My S. tinanti, on the other hand are wild-caught, so I selected a group of eight from a local aquatic outlet in September this year. They were feeding well but were still a little thin, so I allowed them to fatten up a little using a commercial high-protein dry food, frozen bloodworm and frozen Artemia. Once I was happy with their condition I reverted to a standard feeding regime of algae wafers, sinking pellets and Tetra Prima interspersed with the occasional use of frozen foods. I kept a group of four S. casuarius in a 48 inch (122cm) long aquarium along with yellowtail tetras (Alestopetersius caudalis), Corydoras catfish and orange finned Laetacara (Laetacara fulvipinnis). Filtration for this tank was provided by an undergravel filter driven by a powerhead. A group of six S. tinanti were also kept in a kept in 48 inch (122cm) long aquarium along with Congo Tetras (Phenacogrammus interruptus) and Synodontis catfish. Filtration for this tank was provided through a combination of an external canister filter and a small internal power filter. The water used in both tanks was prepared using treated rainwater (treated with Kent RO Right and Proper pH 7), which stabilised at a pH of 6.8 and the temperature was maintained at 260C. Then, on 1st December, without any deliberate interference, a pair of S. casuarius and a pair of S. tinanti, inhabiting separate tanks, spawned on the same day! I thought it was a coincidence, but it was pointed out to me that these fish might be stimulated by freshwater from a recent water change and a drop in atmospheric pressure, something I had observed first hand with Corydoras catfish. In hindsight, I had interfered with the fish the previous weekend, both pairs had been transferred into new tanks with fresh rainwater.  I also checked the Barometer recording available on the internet (www.wunderground.com), it confirmed that the pressure had been falling since Monday and had finally bottomed out on Saturday, the day of both spawnings! So, although it wouldn’t be possible to simulate changes in atmospheric pressure in individual tanks, it may be possible to use water changes as a stimulus (with additional assistance from barometric pressure) to trigger spawning of these rheophilic cichlids.  As I write in early December, the eggs have now hatched and are wriggling in the bottom of their caves. The parents guard them proudly and are preparing additional caves for the young. By the time you read this, I will hopefully have some juveniles ready for the next BCA auction!  Etymology Steatocranus = Greek, steatos – hard fat + Greek, cranus – skull. In reference to the nuchal hump of male fish. casuarius = derived from the Malaysian word casuar meaning Cassowary in reference to the nuchal hump, which looks like the hump on the head of the Cassowary. tinanti = Greek, tin – stretch + Latin, antiae – forelock. In reference to the elongated head of this species. References Lamboj, A. (2004) The cichlid fishes of Western Africa. Bornheim, Germany: Birgit Schmettkamp Verlag. Copyright Text and photos; Simon Morgan This article first appeared in the B.C.A. publication "Cichlidae". ( For B.C.A. info see link on Cichlids articles home page) My thanks to Simon for his article, especially as it from the S.E. of England. A very welcome contributor from outside my inferred "Northern" limits! Can I emphasise that I welcome articles from anywhere in Great Britain (or even from Abroad!) East Anglia Cichlid Group Simon is a member of the East Anglia Cichlid Group. If you live in this general area of England or are a Cichlid enthusiast, do get in touch with the group for any further information re. membership or auctions. CONTACT;- e-mail eacg@ymail.com |
|
<<--- Back to articles list
|