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Fish to Avoid in a Community Setting

There are a number of fish that have gained a reputation as good additions to community aquariums. It is important to research a species of fish to understand their diet and temperament before adding them to a community situation. The following fish should be treated with caution; this doesn't mean that they can't be kept, it just means that without the correct tank size, suitable tank mates and specific conditions they may become problematic.


This cichlid can grow quite large; 6 inches from top to bottom is not uncommon. Some can be quite aggressive with their tank mates. They have long flowing fins and are fairly slow moving, both of which make them an ideal target for fin nippers. This may attract smaller fish; and like most fish, angels regard any fish small enough to be eaten as potential food - it is quite common for neon tetras and similar fish to disappear when there is a large angel around.

Mollies (All types)

Mollies are a brackish type and depend on some salt water to survive; without salt their health will suffer in the long term, and apart from salt they also require a high pH and hard water. These are conditions that do not suit most other community fish, because of this they should not be kept with other fish that require almost completely opposite water chemistry.


These fish are very eager to fight, particularly with their own or related species. They have a tendency to chase other fish, almost to the point of exhaustion. Although there is usually no actual harm done, any fish that is constantly being harassed will begin to show signs of stress and will suffer from stress-related health problems.

Giant danios

Because of their size, speed and appetite, Giant danios have gained a reputation for eating smaller fish, most commonly tetras.

Siamese fighters

Naturally, these are solitary fish. Males will fight at the sight of another male; females will occasionally do so as well. Most of the time other fish are left alone, but, like angelfish, they often fall victim to fin nippers. For maximum success, keep a single fighter rather than a pair and choose tank mates well, avoiding potential fin nippers.

Tiger barbs

Tigers are notorious for fin nipping and may attack tank mates if they are not able to defend themselves. They should be kept in a group, leaving them to squabble amongst themselves. Even in this setting, angelfish, Siamese fighters, guppies or any other slow moving, long finned fish would still be targeted.

When starting a community tank it is a good idea to make a written selection of fish that have all been researched and that all require the same water chemistry, have a similar temperament, and are generally the same size. Always properly research a type of fish before you purchase one.

Following these simple guidelines will help you build a community that is a pleasure to have, rather than one that goes from one problem to the next.

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