Julidochromis marlieri is a fun, torpedo-shaped rock-dwelling cichlid from Lake Tanganyika. Members of this genus are affectionately known as "Julies." Julies make a great addition to almost any rift lake setup. They are fairly tolerant of most water conditions and play well with others, with the exception of conspecifics. J. marlieri has a truly endearing personality. They are like little remote-control subs. They swim sideways, hang upside down, and move in such deliberate motions. The way they move up and down through the rocks is reminiscent of a little hummingbird.
In the wild, J. marlieri inhabits the rocky shores of Lake Tanganyika where there are steep to medium drop-offs of 5-30 meters. They spend most of their time in the caves and crevices of these rocks hunting for food or seeking protection. It is also within these rocky crevices that they spawn and lay their eggs. In captivity, Julies are somewhat shy, sticking to the rocks in the back of the tank and only dash out for food if they feel safe doing so. Needless to say, they require lots of rockwork.
Even though J. marlieri is relatively shy, they can be aggressive towards their tank mates while guarding their territory. One thing that sets Julies apart from most other Cichlids is that as they begin to mature, they will pair off. Julies are not polygamous; instead these pairing relationships remain intact for their entire lifetimes.
Once a pair has formed, it is strongly advised not to change the arrangement of the rocks because these mark the boundaries of the territories of both the male and the female. It is also rumored that any change in décor stresses them out and the stronger of the two will kill the other.
When selecting your first set of Julies, it is best to purchase somewhere between six and ten juveniles. All should be from the same locale (Magara, Halembe, Kala, Katili, Samazi, Kambwimba, Isanga, Cape Tembwe, or Katoto) and from as many different sources as possible in an effort to avoid hybridization. Eventually, a pair from these will form, at which time all others should be either moved to another tank (where more pairs may develop) or sold off. Once a pair is formed, males will aggressively chase off any other females, and the female will chase off other rival females and all other males. Therefore, to minimize aggression, it is best to remove any remaining fish from this same species.
Spawning will begin after pair formation. The dominant male will become more aggressive as he starts claiming territories and defending them. The male will pick a dark cave in a secluded part of the tank. After enticing the female to enter, she will lay her eggs on the ceiling of the cave and the male will pass over them, depositing his milt. The eggs tend to be scattered and not grouped as might be expected. They are much smaller than the eggs of mouthbrooding cichlids, being about 1.2 mm in diameter and are bluish-green in color. Typical spawns number between 50 and 100 eggs. J. marlieri will continue to spawn every five to seven weeks.
Julies are excellent parents, and will guard their young from any intruders or potential threats. When it comes time to eat, one of the two parents will always stay back to guard them. While Julies take excellent care of their young, you might find that only about 10% will survive the first couple of months. If they are removed and given special care (such as baby brine shrimp), you can expect a survival rate closer to 100%.
These cichlids grow rather slowly. After two months, fry will measure about 2 cm long. Unlike the Mbuna and many other cichlids from Lake Malawi, females of this genus are typically longer and more robust than males. Females usually grow to 14cm in length, while males only grow to 12cm. Males also possess shorter, more pointed genital papillae, angled caudally. Females’ genital papillae are longer and more flat on the end than males’, probably for attaching eggs to the surface.
In the wild, J. marlieri is primarily predatory, preying on mostly small snails, although they do need some vegetable matter in their diet. In the aquarium environment, live or frozen Cyclops and Daphnia are recommended. For larger individuals, the European Shrimp Mix, Mysis, and Brine Shrimp are the best foods. Mysis should be fed sparingly, however, because of its high fat content (30%).
The minimum tank size should be a 15-gallon aquarium for a single pair, but if more than one pair are kept in the same aquarium, 75 gallons is the smallest recommended size. As mentioned previously, these fish require lots of rockwork to create plenty of hiding places. If kept without sufficient shelter, it is unlikely that they will develop their best color and will not spawn as frequently as they otherwise would. A fine gravel or sand should be used for substrate. Fry of this species have been known to get trapped in gravel that is too large.