Preventative Medicine for Pet Fish:
In terrestrial veterinary practice "preventive medicine" is often erroneously considered synonymous with vaccination and "deworming" schedules. Of course, preventive medicine encompasses much more, including provision of proper nutrition, maintenance of a healthy environment, and management of other disease risk factors. For pet tropical fish, the lack of available vaccines and well worked out chemical prophylaxis regimens greatly increases the importance of the "other" areas of preventive medicine. Preventive medicine should begin before the pet fish owner sets up their tank or pond, and includes many areas considered "Husbandry".
I. Tank Set-up and Operation:
Proper set up of the tank that will house pet fishes is critical to long term success. For example, tanks set up in southern or western exposure windows may experience severe algal problems possibly along with deleterious temperature fluctuations. Although aquarium heaters can stabilize a tank in cooler environments, fewer systems incorporate the chilling equipment required to keep water temperatures from rising in summer. Relocating these tanks before they are established can avoid numerous problems. Judicious use of blinds or curtains can help if relocation is not an option. Tanks located near radiators or other types of heat exchange outlets can experience similar problems. Remember to assess the air quality in the area projected for the tank and particularly the air quality near any planned remote air pump.
The configuration of a tank can have a great impact on its carrying capacity. Tall tanks with low ratios of surface area to water volume are hard to clean and manage, and can properly accommodate a much smaller biomass than a tank of equal gallonage with a great deal of surface area. Also, many beginners want to start out small and work their way up in tank size. Unfortunately small tanks are much more dynamic and difficult to manage than large tanks. the slightest shift in water quality usually results in rapidly fatal situations. Larger tanks respond more slowly. Larger doses of toxic substances are required to reach toxic levels, which gives the owner more time to observe the problem and react. We advise clients to start out with a tank that holds at least 20 and preferably 30 gallons.
Tanks should also be constructed of materials that won't be toxic to the fish. All glass aquaria are constructed from glass and high grade silicone rubber. Older tanks or occasionally very decorative tanks may incorporate metals or other materials that can be a source of chronic toxicity. Similarly, very exotic substrates (sands, rocks, decorations) need to be evaluated to make sure they won't leech toxic substances. This can be an analytical challenge, and may require a skilled geologist or chemist.
II. Water Quality:
Certainly the single most important issue in preventative medicine for pet fishes is water quality. Improper initial start up and water cycling of tanks on biofiltration can result in ammonia and nitrite toxicities. In older more established tanks, improper methods of changing water are often the cause of build ups of toxic wastes or contaminants. Clients often erroneously consider "topping up", or the replacement of water lost to evaporation, as the same thing as a water change. Unfortunately, toxic substances including heavy metals such as copper do not evaporate with the water. Each "topping up" can add more toxicant, and removes none. Slowly the concentrations build up to toxic levels. A classic example would be a long established tank which has been maintained the same way for years. Now fish are dying, either individually or in small groups. They don't respond to pet store medications and infectious disease signs are not the principle signs. Water change requires that you remove water first then replace water to the original level (0.75% change per day, 10% every two weeks, or 20% change each month will work well in most cases).
The ideal pH level of freshwater aquariums is between 6.5 and 7.5.
Marine tropical fishes thrive at a pH of between 8.0 and 8.3.
The ideal temperature for most freshwater tropical fish is be between 76 and 80 degrees F.
Abnormal Behavioral Patterns
As in terrestrial pets, fish behavior can be a sign of trouble and a cause of trouble. The following is a list of some of the common behavioral patterns displayed by stressed or diseased fish in aquaria.
External Parasites of Fish:
Internal parasites can be clinically significant in aquarium fish.
Metazoan parasites include the skin and gill flukes (monogeneans), cestodes (tapeworms), nematodes, trematodes, and crustacean parasites. With the exception of a severe monogenean skin and gill infestation the presence of these parasites usually does not constitute an emergency. Antemortem fecal examination or a thorough autopsy will diagnose an internal helminth problem.
Most bacterial pathogens of fishes are gram negative rods and include such genera as Aeromonas, Pseudomonas, Vibrio, and Flexibacter. Infections can be severe and lethal.
Once a diagnosis of bacterial disease has been made or is at least suspected, a treatment plan should be formulated. Larger pet fishes may be injected intraperitoneally or intramuscularly with antibiotics which are effective against gram negative pathogens.
An alternative to injectable antibiotic therapy is utilizing the oral route. Antibiotics may be mixed into a gelatinized food or given by force feeding.
Recipe for Gelatinized Food-
A third and less desirable approach to chemotherapy is to administer the treatment as a bath. Antibiotics and other compounds can be added directly to the water. This type of treatment is more appropriate for ectoparasite infections. Fish treated in this manner should be removed from the display aquarium and placed in a hospital tank. The treatment tank should be well aerated and any carbon filtration should be discontinued.
At the present time there are only 6 compounds (four active ingredients) approved by the Food and Drug Administration (FDA) for use in aquatic species, and use is extremely limited in terms of species, indication and route of administration. Approved products include one ectoparasiticide (formalin), one anesthetic (methane tricaine sulfonate) and two antibiotics (oxytetracycline and a potentiated sulfonamide). Certain products have been designated to be of low regulatory priority by FDA which suggests that, while not approved, their use is being tolerated by the agency.
When a single fish is ill, the fish usually can be placed in a hospital tank for treating. In cases in which many or all fish are affected, especially with a condition like Ichthyopthirius ("Ich") and Cryptocaryon (saltwater "Ich") the entire tank should be treated.
During anytime of display tank treatment, carbon filtration should be discontinued because it nullifies the treatment. If the tank contains a viable biological filter, it should be disabled during the treatment to protect nitrifying bacteria. After the treatment, 30% to 50% of the water in the tank should be changed.
Please feel free to contact your veterinarian's office if you have any questions regarding your tropical fish. They will do their very best to assist you in the proper correction of the problem at hand.
Best of luck and we hope you enjoy your tropical fish for years to come. Please check the numerous literature sources available for more detailed information on tropical fish and their care.
David E. Hammett, DVM
G. Scott Russell, DVM
and the staff of All Creatures Veterinary Clinic, PC
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