Aquarium Fish Health Management
IAAAM 1986
R. Francis Floyd; M. H. Beleau
College of Veterinary Medicine and Delta Branch Experiment Station, Mississippi State University, Stoneville, MS


Health management of aquarium fish is receiving more attention from hobbyists and commercial oceanaria as the financial investments in both fish and elaborate exhibits increase. Although the value of an individual fish may be sufficient to justify specific diagnostic tests and therapy, preventive medicine remains the key to aquatic animal health. A program in fish health management is outlined which emphasizes attention to 4 factors: the fish, the water, the container, and nutrition. Techniques for proper quarantine, non-invasive examination, and sample submission of freshwater and marine fish are presented.


Fish health management is receiving increased attention by both hobbyists and professionals. The home aquarium business is experiencing a record "boom!' with retail sales of livestock, food and other products increasing from $547 million in 1983 to more than $673 million in 1984. For comparison, 1984 sales of puppies, dog food and related products was $459 million and bird-related sales were $228 million (1). Commercial oceanaria are also placing increased emphasis on fish exhibits. For example, one major institution invests an estimated $0.5 million per year in "effort hours" to take fish through an extensive quarantine procedure and maintain fish health once they are on display. Value of individual fish may be sufficient to justify specific diagnostic tests and therapy, hut preventive medicine remains paramount to maintaining health in an aquatic system and avoiding disease outbreaks.

Infectious diseases are associated with interactions involving a susceptible host, a pathogenic organism , and an environment which is conducive to both the enhancement of the pathogenicity of the etiologic agent and decreased efficiency of host defenses. To avoid this situation a program in preventive medicine can be implemented with specific and constant attention to 4 factors: the fish, the water, the container and nutrition.



The home aquarist will most frequently purchase pet fish and supplies from a local retailer. Selection of a conscientious retailer who is knowledgeable in fish health may decrease the chances of purchasing sick or subclinically infected fish.

Commercial aquaria may find it cost-effective to capture and ship their own fish to improve survivability. Capture techniques may vary, but handling of fish should be gentle. Efforts should be made to minimize net damage at capture, to minimize drug use, and to hold fish on-Bite 2 to 4 days. Holding fish prior to shipment allows an opportunity to cull noticeably unhealthy specimens and also allows fish to empty their intestinal tract resulting in decreased fouling of water during transit.

Quarantine Protocols

Newly obtained fish should never be placed directly into an established aquarium. Many species of freshwater tropical fish are pond-raised and as such would be expected to have some degree of parasite infestation. Wildcaught marine fish would also be expected to harbor parasites or other infectious agents endemic to their area. The stress of shipment and handling may be sufficient for these fish to develop overt disease if they were previously infected at the subclinical level. In addition, they become a source of infection for fish and environment in an established community. In general, quarantine treatments are designed to eliminate parasitic infestations; antibiotics are only used when bacterial disease becomes evident. Specific tanks should be set aside for hospital or quarantine use (2). Ideally, these should have an external filter, good aeration so that chemicals or drugs may be applied, and no substrate (2). Biological filtration may be supplied by placing conditioned substrate in a porous material (is. nylon stocking) in the back of the tank (3).

Several quarantine protocols are outlined below:

1.  Freshwater Aquarium Fish

a.  Duration of Quarantine: 14 Days (minimum)

b.  Specific treatments:

c.  Days 1-4: Observation with no treatment

d.  Days 5, 10, 15:

i.  75 mg/1 formaldehyde (vigorous aeration)

ii.  6 mg/1 Flagyl@ (metronidazole, 1-250 mg capsule per 38 1 (10 gal) of water)

iii.  Turn off undergravel filter if applicable

iv.  Change water after 5-8 hours
Note: If unable to quarantine new specimens, the following prophylactic treatment may be applied to the display tank following introduction of the fish (4):

v.  75 mg/l formaldehyde (vigorous aeration)

vi.  6 mg/l metronidazole

vii.  Turn off undergravel filter, if applicable

viii.  Change water after 5-8 hrs

2.  Marine Aquarium Fish

a.  Duration of Quarantine: 10 days (minimum)

b.  Specific Treatments:

c.  Days 1-10: -- 0.1 to 0.2 mg/l Copper

d.  Days 10: -- Freshwater bath, pH 8.3

i.  Formaldehyde 150 mg/l (aerate vigorously)

ii.  Leave in bath until fish show signs of stress (usually 15 to 60 minutes)

iii.  Pour off water, catch fish in glass beaker and place in main tank

3.  Marine fish for display in Commercial Oceanaria

a.  Duration of Quarantine: 6 weeks (minimum)

b.  Specific Treatments:
Week 1: A) if ciliated protozoans are of concern give freshwater dips daily far several days B) Allow fish to rest and acclimate to system
Week 2-4: Introduce copper and gradually increase concentration to 0.15 mg/l over 3 days, leave at this level for 3 weeks. Note: If bacterial disease becomes evident before or during copper treatment, stop and clear up infection before proceeding.
Week 5: Allow fish to rest with no chemical stress to enhance immunocompetence.
Week 6: Expose to system water and watch for disease. (This may be considered an active immunization process as once fish are placed in a large tank with many species of fish and invertebrates they may be susceptible to endemic disease agents.)

Examination Protocols

Daily attention to behavior and feeding activity frequently allows the careful observer to identify potentially sick or ill-adapted fish. If disease is suspected, a sick fish can be examined without sacrificing the animal assuming proper care is taken. It is best to obtain a good clinical history and water for analysis before beginning the examination.

Most fish can be lightly anesthetized using MS-222 (Tricaine Methane Sulfonate) (5). Once the fish becomes quiet, careful physical examination can be performed, remembering to inspect the gills. A gill biopsy and scale scraping should be taken for ectoparasite examination. Fin biopsies may be indicated in some situations and can be done at this time. Fecal samples can be evaluated for the presence of internal parasites. Other techniques which have been successfully adapted to fish diagnostics include ultrasound and radiology.


An aquatic animal is unique in that it is constantly bathed in its own or other pollutants. Fish are ectothermic animals and are sensitive to sudden changes in water temperature which affect metabolism and immunocompetence. Water quality specifically must be constantly emphasized and is one of the most important factors in a successful fish health program. Also, different species of fish have different environmental requirements and these must be specifically addressed in each system. Know your fish and know your water!


Most display aquaria are constructed of glass and sealed with inert silicone to prevent leakage (6). Plastic airflow systems are popular and should be placed so that no "dead spots" occur. Quartz gravel is commonly used for substrate material but volcanic rock may also be acceptable.

Materials to avoid during tank construction include lead-based silicone frequently used by plumbers, vinyl, heavy metals or glues which may be toxic. Improperly sealed concrete may cause problems with excessively alkaline pH as limestone leaches into the system. Sedimentary rock, which may seem attractive as a substrate, should be avoided as toxic compounds may be released into the system.

Mechanical, biological and chemical filtration should be provided and various devices or combination of devices may be used to achieve this. Mechanical filtration allows for removal of solid particles by entrapment (7). Biological filtration allows for removal of toxic nitrogenous compounds by bacteria which become established in substrate and filtration materials (7). Chemical filtration, usually provided by use of activated carbon, is not essential for fish health but is aesthetically appealing in that colored compounds are removed from the water (7). Numerous filter designs are available for home aquarium use and selection should be based on personal needs. Filtration systems in commercial oceanaria will be much more sophisticated and complex but should be designed to meet the same basic criteria. Aeration and consequent water movement are usually provided in association with filter systems.


Optimal nutrition is essential for the growth and well-being of any animal. Exact nutritional requirements of many species of fish are unknown; however, nutritionally adequate pre-packaged flake foods are marketed for many species of home aquarium fish. Supplementation may be provided by feeding par-boiled zucchini (which can be frozen for easy storage) for extra vitamin C, and earthworms which have been purged in clean water, can be chopped into an appropriate size for feeding (3). Special diets can be prepared as needed. Always avoid over-feeding and its deleterious effects on water quality.

Sample Submission

It is appropriate to consider the importance of clinical history, sample fish and sample water for a complete evaluation of a fish disease problem. History can be crucial to identifying the source of a fish health problem. A proper interview should include extensive questions about the environment; for example, type(s) of filtration used, frequency of water changes and specific procedural questions on how the aquarium is managed. Ideally, at least one visit to examine the aquarium system would be undertaken. Questions about the fish would include any changes in behavior including aggression, feeding activity, or unusual behaviors such as "flashing", spiraling and changes in activity level. It is important to know if just one fish or the entire community is affected and for how long. Any previous treatments, changes in water quality or temperature, or addition of new fish to the tank should be noted.

Because fish decompose very rapidly once they have died, live, sick fish are best for examination (8). Fish may be transported in plastic bags, half-filled with water and then blown up with air before sealing (9). During transit they should be placed in an opaque container and protected from thermal shock. A water sample should always be provided for analysis. If transit time is to be less than an hour, water from the treatment bag will be acceptable. Otherwise a separate container with the sample water should be provided.


Aquarium fish health management can be achieved by circumventing disease outbreaks through proper implementation of preventive medicine principles. Prevention rather than treatment of disease outbreaks is the objective because even under optimal circumstances treatments are often stressful for both fish and aquarists. Constant attention to fish and environment should pay-off with fewer disease problems and a more trouble-free exhibit. Providing historical information and appropriate samples when disease does occur will aid the fish health specialist in accurate diagnosis and application of appropriate therapy.


The authors thank Dr. Michael Stoskopf and Dr. John Gratzik for their assistance.


1.  Kowalski, D. D. The 1984 pet retail sales survey. Pets/Supplies/Marketing. July, 1985.

2.  Dulin, M. P. Diseases of Marine Aquarium Fishes. TFH Publications, Neptune City, NJ. 1976, p. 53.

3.  Gratzek, J. B. Problem solving approach to pet fish diseases. Eastern States Veterinary Conference. Orlando, FL. Jan., 1986.

4.  Gratzek, J. B. How to get goldfish off to a good start. Pets/Supplies/Marketing. Mar., 1986, pp. 18-24.

5.  Healy, E. G. Anesthesia of fishes. In: Small Animal Anesthesia. Pergamon Press, Oxford. 1964, pp. 59-70.

6.  Oestmann, D. J. Environmental and disease problems in ornamental marine aquariums. The Compendium on Continuing Education, 7(8):656-662. (1985)

7.  Andrews, J. Filtration in a closed marine system. Fish Medicine Workshop, American Association of Zoo Veterinarians. Scottsdale, AZ. Oct., 1985.

8.  Amos, K. H. (Ed.). Procedures for the Detection and Identification of Certain Fish Pathogens, third edition. Fish Health Section, American Fisheries Society. Corvallis, OR. 1985, p. 4.

9.  Wallach, J. D. and Boever, W. J. Tropical fish. In: Diseases of Exotic Animals:Medical and Surgical Management. W. B. Saunders Co., Philadelphia, PA. 1983, pp. 1048-1074.

Speaker Information
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M. H. Beleau, DVM, MS

Ruth Francis-Floyd, DVM, MS, DACZM
Department of Large Animal Clinical Sciences
Department of Fisheries and Aquatic Sciences
University of Florida
Gainesville, FL, USA