Q. I bought two jewel fish from my local pet store and put them in my 75-gallon community tank with an assortment of barbs, danios and tetras. While they were in this tank, the jewels were always out and visible until someone approached the tank. Their behavior was very outgoing, but as they grew larger, some of the smaller fish began disappearing. So I decided to move the jewels into a 29-gallon tank well furnished with clay flowerpots, rocks and driftwood. The water temperature in the tank is 73 to 75 degrees Fahrenheit, and filtration is provided by an outside power filter containing carbon.

Since they were put in this tank the jewels only come out if the room is dimly lit and empty of people. This is the only time I can feed them with any expectation that they will eat. Even then, they will only eat canned dog food and earthworms in small amounts.

Why this change in behavior now that they are alone? Is there anything I can do to coax them out of hiding? It isn't much fun having fish I never see! Also, what can you tell me about the spawning behavior and needs of jewel fish?

A Jewel fish, like many cichlids, appear to monitor the behavior of the schooling fish that share their habitat in nature as a means of assessing their own vulnerability to predation. If the fish that share their habitat are swimming freely about, the cichlids can feel secure that no predators are about. If and when these schooling fish abruptly disappear, cichlids take cover. Those that fail to take such hints rarely live long enough to breed, so this behavior remains strong over generations.

Students of animal behavior and aquarists alike have long used such "dither" fish to overcome the shyness of cichlids in an aquarium setting and elicit the the full range of their fascinating behaviors. You were inadvertently using the dither principle to overcome the shyness of your new arrivals when you placed them in your community tank. The problem, as you have discovered, is choosing companions whose size and behavior allows them to function effectively in this role with minimum risk of making a one-way career shift from dither fish to live food!

Jewel fish are efficient predators, but their relatively small mouths and modest adult size limit their selection of potential prey. Typically, sexually inactive individuals of these Hemichromis species will ignore schooling companions two-thirds their own length or larger. This affords you a pretty wide selection of possible dither fish for your 29-gallon tank. If you strive for biogeographic accuracy in your aquarium fish, both Brycinus longipinnis, the African longfin tetra, or Phenacogrammus interruptus, the Congo tetra, grow too large to make a convenient mouthful for any of the so-called "red jewel fishes."

If you do not mind housing fishes from different parts of the world together, you have many more options to choose from. From South America, Buenos Aires tetras (Hemigrammus caudovittatus) are large and fast enough to stay out of harm's way, as are the silver dollars of the genera Myleus and Metynnis. From Southeast Asia, suitable dither species include Danio aequipinnatus, the giant danio, and mid-size barb species, like Barbus filamentosus, B. everetti and B. lateristriga. Finally, good-sized specimens of such Australasian rainbowfishes as Melanotaenia trifasciata, M. splendida and Glossolepis incissus can also coexist successfully with Hemichromis species.

Hemichromis are substrate-spawning cichlids that typically deposit a compact circular plaque of yellowish-white to olive-green eggs on a flat surface previously scrubbed clean by the pair. Male and female share custodial and hygienic duties, although the male usually devotes more time to defending the integrity of the pair's breeding territory. Both parents are ferociously protective of their mobile fry and will attack and even kill fish too large to eat if their tank is too small to allow such perceived threats to move beyond the pair's territory. Thus, in a 29-gallon aquarium, the presence of dither fish after the cichlids have spawned would be problematic — I would anticipate no problems in your 75-gallon tank.

Hemichromis are not, in my experience, picky eaters. I suspect the behavior you describe is due to the combination of low water temperature and the fact that your isolated pair does not feel comfortable in the 29-gallon tank. You can solve this by introducing suitable dither fish and raising the water temperature about 5 degrees.

Not What They Seem
Q. I am currently keeping several Haplochromis obliquidens from Lake Victoria. I would like to set up this species for propagation, but I have no information on how to do so. In particular, what should the male:female ratio be?

I am currently keeping their water conditions the same as in my Malawi cichlid tanks: pH 8.2, total hardness 7 dKH (120.0 ppm), ammonia and nitrite 0.0 ppm and temperature 75 degrees Fahrenheit. The fish are very colorful and appear to be in excellent condition.

A. I must begin with the observation that the fish you're maintaining are certainly not Haplochromis obliquidens. This species, a specialized grazer on the algae that grow on the stems of aquatic plants, has never been imported into either Europe or North America as an aquarium fish.

The fish usually marketed under the name Haplochromis obliquidens is an undescribed representative of the haplochromine genus Astatotilapia, known to researchers under the handy name of "thick-skin." This species is widely distributed in planted shallow water habitats in both Kenya and Tanzania.

By virtue of its wide distribution, this species displays a fair degree of variation in the number and width of the dark vertical bars present on territorial or courting males. Males of the most commonly encountered aquarium population, which hails from the town of Migori in Kenya, sport four or five very wide lateral bars. This species remains fairly abundant despite the predatory Nile perch, and does not appear to be seriously endangered.

You appear to be caring well for your fish, but water conditions in Lake Victoria are quite different from those in Lakes Tanganyika and Malawi, so I suspect your fish would be a bit happier with a pH closer to 7.0 and the water hardness about half its present level. You are doing a superb job of managing the nitrogen cycle. If you can keep ammonia, nitrite and nitrate at present levels, breeding success with this — or any other cichlid from Lake Victoria — is virtually assured. The only other general husbandry suggestion I would offer you is to include a Spirulina-based flake food in the diet of your fish.

Like other haplochromine cichlids, Astatotilapia "thick-skin" is a maternal mouthbrooder with a markedly polygynous mating system. The association of males and females is restricted to the spawning act itself. The best way to minimize the risk of injury to sexually unreceptive females by overly enthusiastic males is to house these fish on a harem basis — a ratio of one male to as many females as one can find. If you have raised a group of fry to maturity, the sex ratio is probably close to 1:1.

Unless you are housing your fish in a very large aquarium (125 gallons or larger), it is unlikely that it will be big enough to accommodate more than a single territorial male. To ensure the survival of any other males, you should plan on moving them into an all-male tank as soon as they start showing obvious signs of wear and tear.

To maximize the genetic diversity of any fry that are produced, it is advisable to move the male from the breeding tank as soon as you see a receptive female and replace him with another male from the bachelor tank. This gives each male an opportunity to pass his genes on to the next generation.

The developmental period for this species is 14 days at 80 degrees Fahrenheit. Females are superb parents and can be counted on to carry their broods to full term without any need for human intervention.

This is a prolific species — a female around 2 inches (not including the tail) can easily release up to 80 fry. The newly released young measure about 12 millimeters total length, and have no trouble with either Artemia nauplii or finely powdered prepared food as a first meal. With frequent feeding and regular partial water changes, they grow rapidly.

Males can usually be recognized by their larger size, dusky ventrals and well-defined "egg-spot" on the anal fin by eight weeks of age. Females usually begin their reproductive careers between 12 and 16 weeks of age.