Q. I've been keeping a community tank successfully for a while, and now I've purchased a new 20-gallon tank and power filter in anticipation of stocking it with a number of green terror cichlids and perhaps some Corydoras catfish. I assume the cichlids won't bother the catfish, but I'd like to know for sure. I'd like to breed the cichlids eventually. Also, I'm planning on using plastic plants, but would really like to keep live plants with these fish if I can. Is this too much to hope for?

A. Its common name notwithstanding, the fish in the aquarium hobby now known as the green terror is actually not particularly aggressive, at least not by cichlid standards. And I say the fish now known in the aquarium hobby because this has changed over the years. Classified under the scientific name of Aequidens rivulatus, the species originally referred to as the green terror cichlid was a large, brightly colored cichlid from the Pacific slope rivers of southern Colombia, Ecuador and northern Peru. In appearance it was (and is) recognized by a broad iridescent white edging along the vertical fins, and it certainly lived up to its name of green terror.

This fish is actually not seen in the hobby very often these days, and the common name is now used to identify a slightly different fish from the Pacific slopes of Ecuador. It differs from the original species in appearance — with orange vertical fin margins and more metallic green spangling on the head. It is also not quite the terror that the original green terror was.

This species inhabits rather soft water in its home range, so I do not recommend adding it to an African rift lake cichlid tank. It does best when kept in water conditions more closely resembling its natural waters.

This is all moot anyway, because males grow to 8 inches, not including the tail, and thus your 20-gallon tank is only suitable for one individual. I am also somewhat doubtful about the compatibility of green terrors and Corydoras catfish. Something more substantial in size would be more suitable as tankmates. I think you would be better off housing the cichlids with loricariid catfishes, such as bristlenose or clown plecos. Their body armor and spines will provide them with greater protection in the event that the cichlids treat them poorly.

Maintaining live plants in cichlid tanks is always a problem. The green terror does not eat plants, but the digging that goes on prior to spawning inevitably will uproot the plants. You can aquascape their tank quite nicely without using live plants, and indeed, I recommend avoiding live plants unless you feel very strongly about having them in your aquarium. If you simply must have them, I suggest that you try fastening Java fern or small Anubias to pieces of driftwood. Assuming they survive the cichlids, these plants will eventually send roots into the soft wood — once well established they are effectively cichlid-resistant.

I've already noted that your 20-gallon tank is inadequate for more than one green terror, so if you are serious about breeding this species, you will need at least a 55-gallon tank with lots of rockwork and an appropriate-size outside power filter. And, of course, you will need a compatible pair of fish.

As with all monogamous cichlids, which include green terrors, ending up with a pair is best accomplished by purchasing half-a-dozen fry and raising them to maturity in the larger tank you will have set up for them. At any given age the males tend to be larger than females. Even when buying 1-inch juveniles, make sure to select individuals of varying size to ensure obtaining both genders.

Although green terrors can reach 8 inches, they will start breeding long before they get close to this size. In fact, don't be surprised if they begin pairing off at about 3 inches in length, again, not including the tails. The first male and female to pair up will generally make life completely miserable for the other cichlids in the tank.

A 55-gallon tank should be large enough for the pair to create an adequate breeding territory while offering the remaining members of the group sufficient refuge beyond its borders. However, the fish will grow larger, and then it will be necessary to find a new home for the remaining individuals. The popularity of the green terror makes this easy — other hobbyists and dealers will readily take the fish off your hands.

Green terrors are substrate spawners but seem willing to lay their eggs in a variety of locations. Most pairs will readily accept an overturned flowerpot, but others will use a smooth, flat rock. And there are some pairs that do indeed remove the gravel in one spot and place their eggs on the bottom of the tank.

Both the male and female become much darker in color and will become much more aggressive toward tankmates as the time for spawning approaches. When the female's large, white ovipositor becomes visible, you can expect to see eggs within about 24 hours. The first time a young pair of green terrors spawns, their clutch of eggs is likely to be much smaller than the up to 3000 pale-beige eggs that more experienced adults can deposit in a compact circular layer.

As is typical with Aequidens species, the female fans and cleans the eggs and keeps them safe, while the male patrols the boundaries of the breeding territory and makes sure that potential predators are kept at a distance. The eggs should hatch in 72 hours at 78 degrees Fahrenheit.

Typically, the adults will move the wrigglers to pits they have already been digging several times during the four-day period they require to become free-swimming. The fry are large enough to take newly hatched brine shrimp and finely powdered prepared food for their initial meal. A combination of frequent feedings and equally frequent water changes will result in rapid growth. Parental care lasts for about a month.

Look for signs that the female is ready to breed again, such as setting up potential spawning sites. At this point it is best to separate the fry from their parents. If they are not removed, it is likely that one member of the pair will regard the fry as potential predators of the eggs, while the other parent will continue its efforts to protect them. This situation can result in serious conflict between the male and female, and the outcome of this fighting may well result in the death of the smaller of the two partners, the female.

Unless you have access to many large tanks, you will only be able to raise a small number of fry to maturity. The young become progressively less tolerant of each other as they grow older, and this aggression among siblings will result in a significant reduction in the number of fish by the time the fry are six months old. Sexual maturity is usually reached at around nine months, or slightly longer, after spawning.