How to Introduce New Fish to an Aquarium

If environmental conditions are stressful to fish the pendulum of disease will sway in favor of bacterial invasion. If the bacteria multiply in aquarium water as is the case with many types of bacteria, the fish can be exposed to tremendous loads of the organism at once. When the critical mass becomes large enough the fish's protective mechanism may be overwhelmed and clinical signs of an acute disease situation may develop. There are many factors and variables that exist in the disease process. What can you, as the hobbyist, do to reduce the likelihood of creating a disease situation in your aquarium? First consider every object you put in your tank to be contaminated with potentially pathogenic organisms. You can introduce these organisms into your aquarium via new fish, invertebrates, plants, live or unprocessed food, your fingers, and even objects such as seashells. It is of course very tempting to add newly acquired fish directly to the tank but first consider the possible consequences. Why risk in outbreak of disease in your aquarium?

Quarantine and treat your new fish prior to putting it into your tank. A two to three week period of quarantine with several three to five minute freshwater baths will render the new fish free of many types of bacteria. To be on the safe side, consider two to three week quarantines necessary for anything going into the tank and a strict disinfection process such as boiling as necessary for all nonliving ornamental aquarium objects.

The hobbyist should be concerned with all possible sources of infection, modes of transmission of these infectious agents, and the various routes of entry of these organisms. Sources of aquarium infection include both symptomatic and asymptomatic carrier fish. Convalescent carrier fish have clinically recovered from the disease but still harbor the organism. Chronically infected carriers are sick fish that shed the organism on a continuous or intermittent basis. Healthy carriers are healthy fish that excrete the organism thereby serving as a potential source of infection to the rest of the population. In addition to new fish that can bring in organisms, invertebrates, plants and ornaments can also carry disease causing organisms.

Aquarium fish have several modes of transmission of infectious agents. Fish to Fish transmission is most common with water acting as a vehicle of transmission. Sick fish can shed pathogens via wounds or feces or by dying and undergoing decomposition within the tank. As they decompose organisms can be released into the water. Unless a fish eats all or part of the sick fish the vehicle of transmission is the aquarium water itself. Ideally it would be best to know exactly what if any infection the newcomers had, the lifecycle of this bacteria and the preferred method of treatment. Because you as a hobbyist would not find it desirable to sacrifice a number of your fish acquisitions have new fish screened for various infectious diseases; it is safer to assume that all your newcomers are guilty until proven innocent. No harm will come to them if the quarantine procedure is done properly and your established fish will live a longer life because of your new epidemiological perspective.

Citation

The Fascinating Freshwater Fish Book: How to Catch, Keep, and Observe Your Own Native Fish by John R. Quinn p.25-27

The Fascinating Freshwater Fish Book: How to Catch, Keep, and Observe Your Own Native Fish by John R. Quinn p.45-45