What makes Tanganyikans different from keeping Lake Malawi cichlids is the ability to create a
so-called "community tank." This unique trait can
make keeping cichlids a rewarding experience.
In this article we will discuss what
a community tank is. In order to understand how to
create a Tanganyikan community tank we will explore why
this community concept is difficult at best with Lake Malawi
cichlids. We will then discuss how a Tanganyikan
community tank is supposed to work. Finally, we will
conclude our discussion with a few examples of
community setups.
First of all, what is a community tank? In the
broadest sense a community tank is an aquarium in
which the plants and animals therein are all
compatible. This means the tank inhabitants won’t
normally fight with each other nor eat one another. In
other words, you have a harmonious environment where
all plants and fishes are compatible with each other
and should survive and even reproduce over a sustained
period of time.
The number one barrier to harmony in any aquarium is
aggression. Aggression in cichlids is usually the
result of competition for (1) territory or (2) food.
If food is plentiful, and it is in a home aquarium,
the question of territory is the only real concern for
the aquarist wanting to create a community
environment. This is a real problem when trying to
keep cichlids from Lake Malawi. Let me explain with
some examples.
Living among large piles of rocks along the shoreline of Lake Malawi
is a group of cichlids called "Mbuna" (the native name for these fishes). In the aquarium,
mbuna all inhabit the same niche – the rocks and
caves. Realistically, only a few mbuna will be
permitted to claim a residence among the rocks in an
aquarium because there is a limit to space. Those
mbuna left without the protection of a cave make for
easy targets by the more dominant and aggressive
fishes. Subdominant males will be less likely to
reproduce without a claimed territory of their own.
Brooding females will become overly stressed without
the safety of a cave and their longevity is in
jeopardy. Plants are rarely considered in an aquarium
with mbuna because they have a tendency to eat or
uproot any plants. As you can see, creating harmony
with mbuna is challenging.
While the haplochromines of Lake Malawi (e.g., Cyrtocara moori, Placidochromis electra, Protomelas steveni, etc.) are sometimes compatible with a few select
plants, the "Haps" of Lake Malawi don't lend themselves
to a community environment either. The different Hap species have a strong
tendency to cross breed. Furthermore, the Haps
normally stick to the open water, as opposed to the
mbuna who take to the rocks. This is problematic
because space quickly becomes scarce. For spawning to
take place, spawning sites must be staked out and
nests built. If the tank is overcrowded, spawning is
less likely to occur.
Okay, you're probably thinking, why not mix a few mbuna with some Haps. The reason why this is not recommended (and why it would not make an ideal community tank) is due to a few reasons. First of all, mbuna are aggressive eaters while Haps are usually more relaxed eaters. Mbuna can outeat Haps if kept together. The mbuna will get fat while your Haps thin out. Even if this dietary incompatability could be overcome, differences in temperament make these two groups of cichlids poor tank mates. As already suggested, mbuna have a more aggressive temperament, and some would even say obnoxious. Haps on the other hand are generally milder. If the mbuna out size the Haps, then they will stress the Haps. 
If the Haps on the other hand are larger (Haps outgrow mbuna by several times when mature) they may prey on the mbuna. And assuredly, the fry of the mbuna will be preyed upon by any Haplochromine tank mates.
Sure, these fishes can be mixed and maybe even co-habitate peacefully but the resultant environment is not one of harmony where all fishes will survive and even reproduce over an extended period of time. Only with Tanganyikan cichlids, I propose, can a truly holistic community tank be established.
Remember, the two main barriers to creating a community tank are agression from (1) lack of food and (2) territory disputes. These barriers are easily removed with a Tanganyikan setup if approached correctly. Unlike other east African cichlids, the cichlids of Lake Tanganyika adhere strictly to particular habitats. (This is somewhat of an oversimplification, but holds true for all practical purposes in the aquarium.) Several popular species are immediately excluded from the "community" because they are compatible with only a few select tank mates for reasons we will not discuss here. These include Frontosa, Tropheus, and Petrochromis.
The various habitats are easily recreated in the aquarium. In the aquarium, these habitats are reduced (and simplified) to 4 primary niches: open water, rocks & caves, shells, and open sand. The open water niche is filled by genera like Cyprichromis and Benthochromis. The rocks & caves niche is generally inhabitated by lamprologines, Julidochromis, and the gobies. Shells are occupied by the smaller lamprologines and Telmatochromis. The open sand is then claimed by sandsifting Xenotilapia, Ectodini, and Callochromis.
There are many ways to fill each of these niches! Deciding what fishes to mix is one of the most exciting steps in maintaining a community tank, so we won't steal all of the fun. However, we did want to provide a few specific examples to get you started.
