Cichlid Room Companion

Reducing Cichlid aggression

By , 1996. image

Classification: Behavior.

Cichlids from Eastern Africa, also known as the Rift-Lake Cichlids, have a reputation for being colorful, hardy, and prolific. These attributes make them almost ideal fish for the beginner fishkeeper or hopeful-breeder. While East African cichlids are in general very colorful and highly-resistant to diseases, they are also some of the most notorious aggressors in the Cichlidae family. All cichlids are territorial and some are highly aggressive in the lakes, while in the aquarium, the confines of the smaller environment only help to increase tension and the likelihood of an all-out turf war in your "community." While this is probably one of the hardest aspects of African cichlids to deal with, many ingenious hobbyists have overcome or at least subdued this aggression to the point where a relatively tolerant community can be had. In all honesty, cichlids show their most vibrant colors and pugnacious attitude during disputes, so the goal is not really to destroy ALL this activity, but to limit it to the point where you don't wake up every morning with a "victim" floating at the surface.

One of the simplest aids in reducing tank aggression levels is also one of the most overlooked, simply because it involves a little forethought and planning before the fish are even introduced. This involves selecting species that are compatible with each other. The word "compatible" refers to several factors: water conditions, size, color, aggression/activity level, and finally levels of tank habitation.

Let's start with water condition: it should be obvious that while it is possible to keep fish from very different water conditions in the same tank, none will truely flourish. So, it is always advisable to keep only species of cichlids from the same area with similar water parameters. This includes temperature, pH, and water hardness. The two main "biotopes" of East African fish are Lake Tanganyika and Lake Malawi. It is recommended that you do not mix fish from these two lakes, although many hobbyists limited by tank space have claimed no adverse affects in mixing species.

Size: This may sound like common sense but it is too easy to mistake the size of the fish you buy with the maximum ADULT size. It is advisable to start with juvenile fish and grow them up to size. This allows for better acclimatized fish as well as less of a drain on your wallet as juveniles are only a fraction of the cost of adult specimens. Not to mention, many full-sized specimens are wild-caught and prove more diffcult to keep. Thus, you must do some research in advance on the species you wish to keep and determine their adult size and try and match fish with similar sizes. Be realistic- you might not be able to find 3 or 4 species you like that are EXACTLY 4" long as an adult, but just don't but just don't keep a 10" carnivore with a bite-sized fish. Keeping similar-sized fish will help reduce aggression (as well as predation) by removing the burden of "being the smaller victim."

Color: Aggression in most of the animal kingdom is concentrated torwards members of the same species as these are the true "competition" in terms of survival/breeding. This is no different in Cichlids. How do fish detect other fish of similar species? A good guess would be their bewildering array of colors and patterns. Similarly-colored fish as well as similarly-patterned fish are going to be the most likely target of a fish's aggression. Thus, the obvious thing to do would be to keep fish of very different color and/or pattern. There are certainly enough species with different colors to satisfy even the most discerning aquarist, so keep this in mind when selecting your tank's inhabitants.

Aggression/Activity Level: Not all Cichlids are as aggressive as some of the "bad boys" that have given Cichlids this reputsome of the "bad boys" that have given Cichlids this reputation. Some are downright docile. Thus, it should make sense that keeping an easily terrorized species with a "bruiser" can and usually will result in some bloodshed. Do some research into the levels of aggression of the species you are considering for your tank. Books are not very good at explaining this since experience and observation tends to be a good source. Thus, ask fellow aquarists and look to recent publications, magazines, internet postings, etc. for more detailed information. Levels of Tank Habitation: As every species is somehow unique in their behavior, not all cichlids occupy the same levels in the water column of an aquarium. For example, as in nature, there are certain rock-dwelling species that frequent the rocky coastlines of Lake Tanganyika, such as Neolamprologus species. There are also open-water schoolers in the lake such as Cyprichromis sp. that keep to the upper stratum in an aquarium. And just for variety, there are sand-dweller species that frequent the sandy lake bottom in open areas away from the coastline, such as shelldweller sp. athe coastline, such as shelldweller sp. and Xenotilapia sp. Thus, not every fish will fight for the same niche or cave in the aquarium, and thus this is a good way of selectively controlling territorial disputes. If you are attempting to create a community of Cichlids, it is recommended that that you aquascape the tank with different areas representing different locations in the biotope. For example, in a rift-lake tank, it would be nice to have a high pile of rocks in one part of the tank (to simulate the rocky coastline) while having a sandy open part in another area (to simulate the lake floor). Then, an intermediate area could be included joining these two areas, decorated with small rubble and perhaps snail shells (to provide a shelldweller haven). This would allow you to keep 2 or 3 different species together and minimize the interspecies territorial disputes. Even domesticated fish are drawn to certain features of an aquascape so this is a tool to use with all types of fish.

So, we have seen that a little planning in the selection of "compatible" species will go a long way torwards reduced tank aggression. This is great for people who are still in the planning stages of a new tank, but what can you do if you already have an established tank? Several things. If you haven't already maxed out the number of tanks, you can always isolate rougher pairs or species into what is known as a "species tank" where only one species is represented. This obviously eliminates interspecies quarrels but as we mentioned, most of the aggression in cichlids is torwards your own kind. But, isolating breeding pairs can do a lot to calming the territorial fights that often occur in community tanks. (often depicted as a pair owning 80% of a tank's length, with the other fish all huddled into the remaining 20%)

Two other methods of reducing aggression in an established tank are the use of target fish and "controlled overcrowding." We will look at target fish first.

Target Fish: What is a target fish? The ideal target fish is hardy, built-like-a-tank, fast and agile, and somewhat expendible (if they ever get caught by the aggressor...well, you get the picture.) The role of the target fish is to act as a decoy in the tank to help vent both territorial and breeding aggression. Since the average target fish is faster than any of the Cichlid tankmates, it can better deal with high-speed chases and will more likely escape without harm. A side benefit of using target fish is that it gives the usually dominant male of a breeding pair a diversion and thus keeps his spouse from taking the brunt of the males territorial (and sexual) frustrations. Target fish will also induce better fry-defense, in species that offer any.

Commonly used target fish include zebra danios (and larger danios like the Giant and Pearl with larger Cichlids) and Australian rainbowfish. These fish are generally readily available, reasonable, and very efficient swimmers. These fish are also very adaptable in terms of water conditions so they can be used in a broad range of Cichlid biotopes, from South America to East Africa.

The process referred to as "controlled overcrowding" is not a recommended process for the neophyte aquarist. The hobbyist must be confident in his or her ability to maintain good water quality even under heavy bioloads. UNcontrolled overcrowding is probably one of the top reasons why beginning aquarists' tanks fail. The bioload of the tank exceeds that of the filter and without very frequent water changes, the fish are poisoned and the tank dies off. If you are at the point where you have a reasonably good understanding of the chemical cycles that control your tank water quality, and of the many methods of controlling these cycles, then controlled overcrowding can be very effective in reducing aggression. The process is no more than carefully increasing the number of aggressors in the tank so there are more fish than possible territories and thus territories are not readily formed. Without clear boundaries to defend, the fish become more tolerant of each other and since there are more fish, the aggression is diffused over more targets.

Obviously, overcrowding can quickly cause the demise of your tank. So, careful planning is necessary to increase the abilities of your filtration system to meet the needs of the increased bioload. An almost absolute requirement when overcrowding is a step-up in frequency of water changes. Breeders and advanced hobbyists who use this technique can be found doing daily water changes, whereas the average fishkeeper can get by with weekly or biweekly changes. Filters have to be watched carefully for clogging and cleaned out often. Nitrates build up quickly in an overcrowded tank, and the easiest way to reduce levels is through water changes. So, to summarize, controlled overcrowding (along with increased tank maintenance) can be an effective diffuser of Cichlid aggression in tanks. You should discuss your tank's bioload capabilities with someone who has experience with Cichlids.

In conclusion: We have seen several ways of controlling Cichlid aggression in our tanks. In nature all is not perfect- fish do die from conflicts and disputes. But in tanks, loss of fish is both unpleasant and dangerous to the well-being of a closed aquatic system. Choosing your tank inhabitants carefully will solve 90% of your headache. The last 10% is the *grey* area but the use of target fish and controlled overcrowding can help minimize it. You will never obtain a perfectly peaceful community as it is Cichlid nature to quarrel and fight for territory, as for any animal. It just so happens that Cichlids have evolved into excellent fighters and thus casualties are higher. Follow the tips athe tips above, talk to other experienced aquarists, and you will be much closer to obtaining a tolerant Cichlid biotope.


Sung, Devin. (May 27, 1996). "Reducing Cichlid aggression". Cichlid Room Companion. Retrieved on Oct 04, 2023, from: