Cichlid Aggressiveness.
We love our pets for their pugnacious character; however, this exact trait of American cichlids, commonly grouped under the concept of cichlasomas, is one of the significant difficulties in keeping them. East African cichlids have a reputation for being bright, prolific fish, but with attitude. This combination of qualities makes them very suitable for beginner aquarists and breeders.
But despite the fact that East African cichlids are undoubtedly some of the most vibrant aquarium pets, they also unfortunately have a reputation for being some of the most ruthless “terrorists” in the entire Cichlidae family. An important part of cichlid care is understanding the need to control and limit their aggressive behavior. While it is impossible to stop aggression completely, there are certain methods to influence their behavior.
Many cichlid species are known for their extreme aggression. The relevance of assessing the level of cichlid aggressiveness is highlighted by the conditions of keeping them in an aquarium, which are naturally different from their natural habitats. The manifestation of aggression to one degree or another is characteristic of almost all cichlids, but this should not be viewed as an insurmountable obstacle to keeping them together in an aquarium. All cichlids are territorial one way or another, even in the wild, let alone in aquariums – a smaller volume sometimes pushes their aggressiveness to the limit, and a veritable war begins in the community. So this trait of cichlids significantly complicates their maintenance, yet many aquarists still manage if not to eliminate aggression entirely, then to achieve more or less tolerable conditions of a “cold war”.
However, we must not forget that these fish demonstrate all their splendor precisely when they are “arguing with each other”, so you should not set a goal to completely eradicate their natural territoriality, but rather limit it to safe limits for other fish. Cichlid aggressiveness is not only determined by their natural predisposition, and not so much by it, as it depends on the aquarist themselves, their knowledge, ability to set up the aquarium, select the right fish composition, and make appropriate changes when necessary.
Indeed, if preference is given to large cichlids from the Amazon region, selecting a community whose representatives easily get along not only with each other but also with fish of other families is quite problematic. Aggressiveness, unfortunately, is typical for all Malawi cichlids. Almost all species are territorial and intolerant of competitors. In the confined space of an aquarium, if its inhabitants are fish of such species as, for example, Melanochromis, some Pseudotropheus, Nimbochromis, Protomelas, etc., it is not recommended to keep males other than the dominant one. In some cichlids (Melanochromis auratus, Melanochromis chipokae), even females show aggressiveness. Sometimes (in the case of Aulonocara), the male’s aggression is directed at fish whose coloration is similar to his own.
You should not confuse the size of the individuals you buy with the size of adult fish. Most cichlids sold in pet stores look about the same size, but as they grow older, the differences become obvious. Some small fish bought as babies grow with unexpected speed into eccentric tyrants, delightfully tormenting the aquarium population with endless attacks. It is better to acquire fry, raising them to their maximum size. Young individuals acclimatize to new conditions more easily. Also, do not forget that many adult animals are “wild-caught” specimens brought from their habitats or breeding facilities, which are significantly harder to keep in captivity. Keeping cichlids of similar proportions will help reduce aggressiveness and dampen predatory instincts. It is best to combine fish of similar temperament, habits, and adult size, introducing them together while they are still in the fry stage.
Aquarium stocking level. The aggressiveness of cichlasomas largely depends on the size of the aquarium in which the fish are kept. Notably, most stories about “killer cichlasomas” come from owners of small aquariums (less than 150 liters / ~40 gallons). The larger the aquarium, the calmer the fish behave (from 500 liters / ~130 gallons upwards). Thus, when deciding on the volume, you should be guided not only by the physiological needs of the cichlids, but also by their behavioral traits. It should also be borne in mind that as fish grow, their territorial claims tend to increase. Since each individual displays somewhat unique behavior, not all cichlids occupy the same “floor”.
For example, there are fish that naturally inhabit the rocky shores of Lake Tanganyika, such as Neolamprologus. In the same lake, there are also pelagic species, such as Cyprichromis, which occupy the upper part of the aquarium. And there are those that live in open areas, like Xenotilapia. Their interests do not overlap, meaning not every fish will fight in the aquarium for the exact same cave, which allows you to control their aggression level. If your goal is to create a cichlid community, the aquarium must be set up so that all levels are inhabited. For example, in one corner, you can create a semblance of caves stacked with stones (simulating a shoreline), and in another corner, pour sand (simulating a bottom landscape). Such a layout will allow you to keep representatives of two to three species, significantly reducing the risks of territorial disputes, because even captive-bred individuals remain territorial.
Secondly, you need to distinguish between intraspecific and interspecific aggression, as well as conflicts arising within a breeding pair, as well as manifestations of predatory behavior and territoriality. Types of aggression inherent in some species may be completely uncharacteristic of others. As a telling example, we can mention the severum (Heros severus), known for its strong intraspecific intolerance, but at the same time exceptionally placid towards neighbors of other species, even during the spawning period. In the animal kingdom, aggression is directed primarily towards individuals of one’s own or a closely related species, because the law of the struggle for existence/reproduction comes into play here. All this fully applies to cichlids as well.
How do fish distinguish “friends from foes”? Apparently, color or the presence and arrangement of stripes/spots serves as an indicator here. Similarly colored individuals are most likely to become targets of aggression. For example, if you have vertically striped cichlids, it is best not to have other vertically striped cichlids, even if they differ in color and species.
Thirdly, aggressiveness depends on a number of factors arising both from the natural characteristics of a particular species and the specifics of keeping them in an aquarium. It is believed that fish raised together show less intolerance toward each other than those combined at a mature age. However, regarding American cichlids, this principle works much worse than for Africans, and joint rearing does not guarantee a peaceful life later on when the fish grow up and form pairs. The rigid “prison-type” hierarchy inherent in Malawi cichlids, angelfish, discus, and uaru is not characteristic of cichlasomas.
A species tank with cichlasomas has a different organization. Here, the analogy of a large communal apartment is more appropriate, where each pair or individual considers itself worthy of a better position, but for a time is forced to put up with what it has. But as soon as you remove one of the fish from the aquarium or introduce a newcomer, a fierce redistribution of positions can begin. Moreover, unlike Malawi cichlids, everyone pounces not on the newcomer, but each on their closest competitor, defending their place in the new hierarchy. However, the most problematic for co-keeping are fish that have spent a long time alone beforehand. It can be difficult to even find a partner for such individuals. Some males become simply pathologically aggressive.
Even more explosive is the desire of one of the pairs to have offspring. At the same time, future parents receive an additional “bonus” of strength, allowing them to perform actions they would never dare to do in normal life. Accordingly, their combativeness increases greatly. Some species, such as the convict cichlid (Archocentrus nigrofasciatus), limit themselves to claiming a corner and then escorting their fry around an aquarium populated by other fish, handing out swats left and right.
Other species strive to take over the entire aquarium at once and, conversely, corner their neighbors, beating them severely the moment they twitch (Jack Dempsey cichlids), or simply getting rid of neighbors entirely (olf-stripe cichlids). Removing pairs preparing to spawn will help solve this problem, as such fish occupy up to 80% of the aquarium volume, while the rest are forced to crowd into the remaining 20%.
An important factor is the availability of hiding places. It is always recommended to have grottos, stones, driftwood, and various ceramic items in the aquarium. The more objects you arrange in the aquarium, even if they do not go all the way from the bottom to the top, the easier it is for the fish to divide the entire space. Driftwood is very important. These should not just be sticks or slabs of wood, but good, twisty pieces of driftwood, preferably reaching from the bottom all the way to the surface. They should intertwine, creating openings appropriate for the fish’s size, through which the fish can maneuver freely. One corner cluttered with driftwood is not a solution; the strongest pair will take it, and the rest will remain without shelter. The less often a victim catches the eye of its abuser, the lower the danger of being attacked. However, another important point is often overlooked.
The aquarium setup should provide not only for the convenience of hiding, but also of swimming – the freedom to flee. There should be both “barricaded” and open areas, and decorations should not have sharp edges so that fish chasing each other do not accidentally get hurt. However, neither hiding nor fleeing on their own can save a fish from an energetic pursuer. If the pursuer is serious about dealing with its competitor, it will eventually happen. This is usually preceded by harassment, nipping of the sides and fins. Thus, the aggressor warns its owner of its intention to get rid of the neighbor. And only after some time does the lethal attack follow. The presence of shelters can significantly prolong this period, but not make it infinite. Therefore, you should not let things drift. If you see that a fish is being badly beaten, it is best to remove it.
And finally, age. It is believed that the most “injury-prone” period is the first adult year. Mature individuals become more “sensible” and lazy. But this applies more to Central American species. Severums do not get wiser with age, but their temperament tends to deteriorate.
Reducing Cichlid Aggressiveness.
Dominance in a Cichlid School. The Dominance Factor. 
