Create a Compatible Tropical Fish and Invertebrate Community
The compatibility of your tropical fish is one of the most critical factors in keeping a successful aquarium environment. Basically put, if your fish don’t get along, they can injure themselves or their tankmates, leading to infections and even death. By properly preselecting the correct combinations of fish species, you can avoid the territorial disputes that much tropical fish have.
Also, let’s always remember the Golden Rule of Fish Size – “If a fish has a mouth big enough to swallow another fish, it eventually will.” Besides fish size, the aggressiveness of one species versus the next is usually the deciding factor on how well everyone in your aquarium will get along. Do not put most African cichlids in with Ram cichlids – odds are high that the Ram cichlids will be harassed extensively, causing great stress and eventually death.
To make sure that you are choosing the correct blend of species for your aquarium, use the chart below as a guide to which fish can get along with each other the best. This chart is not the final word, as every fish has a different personality, but use it as a baseline to determine the potential aggressiveness of your new fish. It is very important to understand that all aquarium fish have different temperaments and personalities. Simply because two fish are classified in the same category of aggressiveness does not always guarantee compatibility, either. However, let’s begin by discussing Fish Tank Guy’s 6 major categories of fish aggression:
This class of fish tends to prefer to be alone. It is easily intimidated by other species, even possibly by its own type except during breeding time. These fish are usually very inactive or may be predominantly nocturnal so they may hide under the cover of darkness. Solitary species do not like to interact with other fish and are scared by sudden movement. These fish do not do well in an aquarium that is located in a high-traffic area such as an office waiting room or living room of your home.
Few fish fall into this category and are usually kept by those who understand that these species need delicate care and solitude to eliminate stress. The elephant nose is a good example of a solitary species since it is blind and relies on Electronavigational to find its way around. This fish hides in any tight space that it can back into and feel protected from others. Even though the elephant nose is classed by most as a timid or even a community fish, it requires special attention and really does prefer total solitude.
Tropical fish in this group are usually very shy and like to school together with others of the same species. Neon tetras are a fine example of a member of the timid class since they are easily victimized by larger or more aggressive species, and they prefer to swim around in large schools of 30 or more.
The most common category of fish communities is the “community fish”. This large selection of common tropical fish species tends to get along quite well with each other and does not usually establish significant territories unless they are breeding. Many of this class are livebearers, or fish that give birth to live fry, and can breed “on the run” without needing to build nests or dig breeding pits. Aquarium hobbyists are very familiar with the major members of this grouping: tetras, mollies, swordtails, platies, guppies, and angelfish. It is still important to remember the golden rule about fish size: if a fish has a mouth big enough to swallow a tankmate, it eventually will.
Fish in this category are beginning to establish defined territories in the aquarium and defend them. Semi-aggressive fish can be passive most of their lives, but can also turn on tankmates and cause injury or death to others. Fish in this classification will normally establish a territory near a particular decoration or location in your aquarium and defend that territory from invaders if it feels threatened. Keeping a large density of these fish tends to keep them from establishing territories and keeps them more passive. These fish like to take bites out of their tankmate’s fins in an effort to prove their point.
This class of tropical fish is saved mostly for the cichlids and larger catfish. Aggressive fish will establish defined territories and keep all others away from their turf and breeding grounds with full force. Members in this category will usually fight among each other but may be kept from establishing defined territories by keeping them in dense groups. Adding new members to an aggressive and established aquarium is almost a death sentence for the new fish.
Even the smallest of aggressive fish will attack a new member even many times their size in order to defend their turf or new offspring. By introducing aggressive fish all at once, none of the members should be able to successfully establish a set territory, keeping them more passive than usual. Fin biting with this group is common, usually picking on the weakest member of the aquarium.
The most commonly known of all extremely aggressive is the piranha, which is actually a myth. The piranha is actually a semi-aggressive to community species, feeding on some protein but normally using its teeth to tear up plants. The piranha normally becomes an extreme aggressor only when the school is starving and trapped in a receding pool of water, where their teeth are then used to tear flesh instead of plant roots.
Other extremely aggressive tropical fish include large South American cichlids such as red devils, Oscars, and convicts which grow large and eat whatever fits in their mouths. Without being given proper room to establish territories, this class of fish personality will attack usually to death.
See More: Freshwater Tropical Fish Species From Around the World