By Donna M. Recktenwalt
We’ve all seen it. We turn on the lights in the fishroom unexpectedly, we move too quickly when working near a tank, or we’re trying to net a specific fish, and all the fish in the tank suddenly go crazy, darting wildly and often stunning themselves against the glass.
This disconcerting “fright response” is a natural defense of the fish against predators. While the sudden darting activity confuses a predator, the fish is also releasing chemicals into the water that alert others of its species to the danger. This is why one frightened fish in a tank can set off all the rest. In the artificial environment of an aquarium, this panicky behavior can result in fish dying from shock, or in some species, in numerous individuals jumping out of the tank altogether.
In general, fish that are comfortable in their environment will rarely panic. Most observed panic behavior occurs when the fish are first introduced to a new environment (as from a planted tank to a bare breeding tank, for example), or when their environment or its social dynamics are changed dramatically, such as with the addition of new fish.
How best to prevent panic attacks? Make the fish feel more secure. In most species, the more secure the fish feel, the more freely they will move around their environment and the less inclined they will be to panic. The following are a few methods to reduce stress and promote security in your fish.
Provide Cover and Hiding Places
Bare tanks can cause distress for many fish. Whether rooted or floating, the addition of plants or mops make most fish feel more secure. You can also provide hiding places, in the form of tank decorations such as root wood, small flower pots or similar materials.
Add opaque dividers between tanks, and create a “bottom”
Sometimes just seeing a possible threat in the next tank makes fish nervous. To prevent this, slide a sheet of dark colored paper or cardboard between the tanks, or tape paper to the sides and/or back of a tank. Some breeders go so far as to paint three sides of their tanks black, as well as the bottom.
Try adding a thin layer of dark gravel or peat to the bottom of the tank to reduce the reflections and reassure the fish. Usually only a very small quantity is required. An additional benefit of using is the absorption of any “panic” chemicals. This can also be accomplished by using carbon in the filtering system.
Add Dither Fish
Often the presence of another, quieter species in the tank is all that is required to “settle” nervous fish. Some species that have proven effective are Heterandria formosa, guppies, some of the smaller danios, and similar small peaceful species.
— GCKA Newsletter, April 1997