Focusing on Fish
by Curt Nuenighoff
November 1, 2009
Fish are a vital part of many ponds, and pondkeepers who care for fish should pay special attention to water quality and nutrition.



Pond fish are sensitive to a variety of factors that can weaken immune systems and make them susceptible to disease, such as water quality and nutrition. For example, raised pollutant levels (i.e. ammonia, nitrite and nitrate) and sudden changes (or unsuitable values) of water pH and hardness can have adverse effects on fish. In addition, pond fish need the proper combination of protein, fats, fiber, minerals and vitamins. Too much or too little of any particular nutrient can negatively affect the fish.

Fish that live in poor conditions will show severe signs of irritation and occasionally reddening on the skin and fins.  Poor water quality can lead to irritation of the gill and skin membranes, and a reduced ability of blood to transport oxygen. Fish immunity can also be weakened, allowing parasite numbers to increase. These fish are also prone to poor coloration and poor growth.

Raised pollutant levels are generally caused by overcrowding, overfeeding or under-filtrating. Each leads to the imbalance between the number of fish and the amount of filter bacteria, which decompose fish waste. Once identified, pollutant problems are relatively easy to overcome. A large partial water change using de-chlorinated tap water will immediately dilute the problem, giving the pondkeeper time to identify the cause.


Recognizing Unhealthy Fish
Even fish living in a good environment with a nutritionally balanced diet are prone to disease outbreaks from time to time. Factors indicating poor health include gasping, rubbing, becoming darker or lighter in color, appearing emaciated and exhibiting listless behavior. To successfully treat the illness, fishkeepers must observe the fish’s behavior and condition in order to identify the problem and what might be the cause.

If a customer believes there is something wrong with his or her fish, have them bring in a photograph so store employees can identify the cause and offer a remedy. For example, a fish gasping at the water surface indicates it is not getting sufficient oxygen (there is more oxygen in the water at the surface). The cause may be poor water quality, gill parasites or blood parasites. The retailer can then offer treatment. Redness and raised gills might be the sign of a severe bacterial infection, a bulge could be the sign of a tumor and erratic swimming behavior could be the sign of a swim bladder infection. 

Have customers remove and quarantine badly diseased fish to prevent the further spread of disease. In addition, have them supply the store with a water sample to be tested for imbalances. Advise customers to immediately change 50 percent of the water and remove any excess debris, which would otherwise bind with some of the remedy making it less effective.

To treat the pond, use a broad-spectrum remedy that destroys harmful bacteria, parasites and fungus. Advise customers to turn off the UV unit while treating the pond. If an infected fish has been isolated, work with the customer to identify the specific ailment and treat with the appropriate remedy.

Maintaining healthy fish is a mixture of common sense and textbook knowledge. Encourage customers to ask questions when information they collect doesn’t make sense. As knowledgeable and reliable pet experts, retailers can help customers avoid making costly mistakes and be happy with their success as fishkeepers.


Curt Nuenighoff is TetraPond director.