Cichlids are generally considered to be aggressive but there are a still many others of more peaceful cichlid types well suited to the community (mixed species) setting.
A community is an interacting population of various kinds of species in a common location. A community aquarium or tank is a collection of various fish and plant specimens that can thrive and get along well with each other, but do not necessarily share the same origin or geographic regions.
If you intend to stock your community aquarium, you should include fish and plant species from a wide geographic range that have similar wants and needs. This simply means that the fish varieties in your community tank must have the same pH hardness and temperament as the other inhabitants.
Mixing a cichlid community with a small tetra community will only result in a fat cichlid community. It is because many cichlids are predatory towards smaller fish. Some cichlids, such as Apistogramma or Julidochromis spp. are timid in the aquarium.
Having different varieties of fish in your tank adds color to your aquarium. But you have to consider also fish varieties that inhabit different layers or regions of the tank. You will want a fish selection that will include bottom, middle and top dwellers. This will ensure that your aquarium is evenly spaced out.
Your fish tank could have a fish selection that includes lively and sedate fish, nocturnal and diurnal, large and small as long as they all fit into the basic definition of ‘community’.
Your fish tank should not, however, be overcrowded. So how many fish should you put in your tank?
The rule of thumb for fish capacity is between ½ and 1 inch of full grown fish per gallon of water. However, you must take into consideration the displacement of the gravel, sand, and other decorations in the tank. A 20 gallon tank may no longer have a 20 gallon water volume because of the additions.
Cichlids, whether African or South American, are very territorial and they need more space. When mixed with community fish, they should have still more.
Angels and Firemouths seem to adjust well living with community fish but never mix Africans with community fish. The community will vanish in no time. It is often better to have the community tank semi-established before adding your cichlids. They can grow up with community fish around them and will be less likely to see them as their next meal.
Firemouths and Angelfish are among the least aggressive of the cichlid family, but full-grown they have plenty of attitudes! This makes them very interesting to keep, but can also cause conflict.
Angels are fun to keep in the aquarium because they pace the glass when they see you coming. They want to be seen so that they can be fed. They are voracious eaters.
Ideally, a tank should have one bottom feeder, 3 medium fish like danios, 5 small fish like cardinal tetras, and a Firemouth or an angelfish. This tank will not be stretching its oxygen limit.
It will have room for the angelfish/Firemouth to grow to full size. As a rule, a ten gallon tank will only house one full-grown cichlid without conflict. Therefore, when planning a community tank, the more room the cichlids have, the better. Territorial conflict is likely to be less if all parties have to a place to retreat when needed, as they would have in their natural habitat.