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[anchar]

Contemplating Petrochromis
by Jeff Shore

After scraping together some money, I decided I would buy some filter equipment. I called Cory and asked for a fluidised bed filter and a UV steriliser.

He said "Yeah, but I've got some Petrochromis trewavassae for sale."

I said, "I'll have 'em."

Cory said, "Do not worry about buying filters, get the fish and just make extra water changes."

I went down the shop and had a look at these fish and I thought they were awesome. Cory worked out a payment plan and I put down a deposit. The day I was supposed to pick up the fish, I was asked to run an errand. As it turned out some idiot overtook me on the left hand side when I was turning left, and smashed my car. I thought "oh well" smashed car or no smashed car I was getting them fish. Now I have 27 Tropheus sp., 6 Petrochromis sp., 4 Tandanus and a 100 Rainbow fish.

The famous British Ichthyologist, Dr. E. Trewavass was honoured by having Petrochromis trewavassae named after her. Either alone or in collaboration with others, she described 7 cichlid spp. from Lake
Tanganyika.

Habitat
Petrochromis spp. live in the rocky zone between 2 metre and 20 metres deep. It is seldom seen at 20m because there is not enough light to generate the growth of large amounts of filamentous algae needed for their nutrition. The stony coast, at these depths, forms all sorts of plymouths and monoliths that provide the abodes for these organisms.

Water Quality
pH 8.5 - 9.0, kH 350 ppm and temperature 28C

Characteristics
Petrochromis spp. grow to between 150mm for P. famula to 400mm for P. spp. 'giant'. P. trewavassae grows to about 180mm. Female Petrochromis trewavassae remain somewhat
smaller, but they retain rows of white dots for longer. The dots on the male diminish as the fish ages. The background colour of P. trewavassae is brownish purple. They also have a bright orange-yellow mouth. The lips never close, always retaining a gap of about 2.6mm. [u]P. trewavassae[/i] also have innumerable amount of small, tricuspid, teeth on both the upper and lower lips. The body length on average is about 3.28 x longer than the height. The outer edge of the caudal fin is lunate, with extensions on the tips, the dorsal, anal and ventral fins also have these extensions. Petrochromis spp. have 3 anal fin spines. Males have 3 or more pseudo-ocelli; females have 2 or less generally.

P. trewavassae is less aggressive than other Petrochromis spp., but is more aggressive than Tropheus annectens. The intestine of a Petrochromis spp. can be 10 times longer than the body length; this gives an adult Petrochromis trewavassae a 1.8M intestine (Konings 1988).

They require a diet consisting of filamentous algae along with spurilina flakes or other high vegetable content flake. They can
tolerate some zooplankton that is sometimes found in amongst the algae filaments. Petrochromis spp. are omnivores, therefore never the less care has to be taken to avoid the onset of bacterial infections.

Captive Requirements
Generally a large tank is required to keep these robust teleosts; 800L would be ideal, but smaller will do. Good filtration is essential. It is best to start with a colony of about 5 (m) and 15 (f), or start with 8 added to a colony of Tropheus spp. It is essential to minimise aggression by setting out the tanks decor so as to set up a pile of rocks that breaks up the line of sight from one end of the tank to the other. If gravel is to be used (I do not use gravel), then it should be fine sand that is natural but clean.

Reproduction
Petrochromis spp. are agamic ovaphile maternal mouth brooders, who show strong aggression intraspecifically. A female may hold a clutch of up to fifty young in her buccal cavity. Eggs of a mature female are 6mm in diameter. Males court females vigorously and constantly. Fertilisation takes place intrabuccaly. At 28C, the eggs hatch and deplete their yolk sac, and are released from their mother’s mouth at 28 days, at which time they would be about 18mm long. The fry can return to the safety of their mother’s mouth if danger threatens them.

The genus comprises 7, maybe 8 species, some with sub-species or geo-varieties. P. ephippium, P. famula, P. fasciolatus, P. macrognathus, P. orthognathus, P. polydon, P. sp."texas", P. trewavassae.

I've had the yapyaps (Petrochromis) for about eight weeks now and everyday I look forward to seeing them. They're always the first to the front of the glass looking for a feed; you can tell they are more intelligent than Tropheus spp. When you peer into the tank for a closer inspection, it is the yapyaps that come up to you and peer back, begging for some food. They haven't shown much aggression towards each other, as they are still young. But I have heard that Petrochromis spp. start fighting in the mother’s mouth. The Tropheus seem to interrupt any bickering that might break out.

The Petrochromis are growing at a steady rate, faster than Tropheus but slower than Mbuna. They spend their day picking and scraping at anything they can get their mouths around. Keeping a healthy supply of algae requires a well lit pond in the backyard. It appears I have 3 males and 3 females at this point but without examining the genital papillae, I'm not certain. The Tropheus seem to accept the new arrivals quite well. Introducing young fish appears to be a lot easier than trying to introduce adult fish to an existing colony.

I will do a more intensive paper on the genus as a whole in the up and coming future.