Volume 55 | Issue 1 Article 4

1993 Medicine Candace J. Carter Iowa State University

Mary Ann Nieves Iowa State University

Follow this and additional works at: https://lib.dr.iastate.edu/iowastate_veterinarian Part of the Small or Companion Animal Medicine Commons

Recommended Citation Carter, Candace J. and Nieves, Mary Ann (1993) "Aquarium Fish Medicine," Iowa State University Veterinarian: Vol. 55 : Iss. 1 , Article 4. Available at: https://lib.dr.iastate.edu/iowastate_veterinarian/vol55/iss1/4

This Article is brought to you for free and open access by the Journals at Iowa State University Digital Repository. It has been accepted for inclusion in Iowa State University Veterinarian by an authorized editor of Iowa State University Digital Repository. For more information, please contact [email protected]. Aquarium Fish Medicine

Candace J. Carter* Mary Ann Nieves, DVM**

Introduction environment. Veterinarians must keep in mind that there are two environmental factors The keeping of ornamental fish may be the dominating the fish's existence: the quality of the most popular animal-oriented hobby in the aquatic environment, and the moderating effect United States. One household in every three of on the metabolic processes of owns and cares for some type of fish. In poikilotherms, especially their defense mecha­ 1985, approximately $200 million was spent on nisms.2 aquarium fish retail sales. An additional $289 If it is necessary to see the patient, clients rnillion was spent on aquarium supplies and should be instructed on what to bring. For another $93 rnillion in fish food. 1 Although some problems involving a full tank of fish, the most ill varieties may be purchases at low prices, people but live specimen should be brought to the clinic. rarely own one fish and the aggregate value of Recent mortalities may be brought as well, but in 'fish in the home aquarium can beconle quite a different container. The live fish should be large. The loss of individual fish may not be transported in enough to allow it to swim expensive, but numerous losses of inexpensive upright and turn around. A container of an equal fish can be costly. The growing number of fish amount of water from the involved tank should hobbyists have few "experts" to turn to when be brought in a separate container. This water aquarium problems arise. Many fish hobbyists may be useful for testing, but more importantly, have other in their households requiring the water can serve as recovery water should the veterinary care, therefore they will frequently patient need to be anesthetized. If the weather is ask for veterinary advice for their 'fish health extremely hot or cold, the contained fish should problems. be insulated.

Evaluating Fish Health Problems Assessing

The basic principles of epizootiology, host­ The major cause of fish and mortality parasite relationships, and environmental control is poor water quality. Water quality is probably are as applicable to fish as other animals. A the most complicated part of aquarium manage­ basic understanding of aquatic husbandry ment and the most important. It is necessary to techniques and can go a long have an understanding of water quality prin­ way for veterinaria.ns with clients who a.re ciples in order to successfully diagnose and . correct aquarium problems. Approaching problems in the aquarium involves the same basic diagnostic principles used for any animal health problem. Changes in behavior frequently offer clues that direct the Oxygen is the most important life supporting evaluation of a problem. Fish tend to show more component found in water. Water contains much immediate reactions to environmental changes less oxygen than air (0.004% in sea water and than do terrestrial because of the 21 % in atmospheric air).3 Most fish need to intimacy which exists between fish and their ventilate a volume of water ten times that of the air ventilated by a land animal to obtain the *Dr. Carter is a 1992 graduate of the College of same amount of oxygen. The amount of oxygen Veterinary Medicine at Iowa State University. dissolved in a given amount of water is depen­ dent upon four factors: temperature, atmo­ **Dr. Nieves is an Assistant Professor of spheric , , and aquatic 3 Veterinary Clinical Sciences at Iowa State life. ,4 In water, oxygen is either saturated, University. supersaturated, or undersaturated. With an

10 Iowa State University Veterinarian adequate aerator most household are saturated and contain plenty of oxygen for Ammonia in water occurs in two forms: toxic the resident 'fish. Supersaturated water can ), unionized ammonia (NH3 and the relatively lead to a disease problem known commonly as non-toxic ionized form (NH The actual 4+). "gas bubble disease," which occurs when proportion of each compound depends on atmospheric gases actually come out of temperature, pressure, salinity, and pH. in the bloodstream of fish. The resulting emboli Generally, the higher the pH, the more union­ can kill the 'fish. This problem can also present ized ammonia present. A good rule to follow is itself as subcutaneous air bubbles on the any unionized ammonia reading greater than affected 'fish. .025 ppm should be considered dangerous over long periods.3 Salt water fish tend to be more

pH sensitive to NH3 than freshwater fish.

pH in itself is not nearly as important as how it is related to other water chemistry parameters Nitrite is an intermediate compound in the such as ammonia. Ammonia below pH 7 is cycle and is converted to by a unlikely to be a problem. Unionized ammonia healthy . Problems usually arise when ) (NH3 is highly toxic to fish and builds up in nitrite levels rise above 1.0 ppm, but levels as alkaline . The normal pH range for low as 0.1 ppm may also affect fish adversely. freshwater fish is 6.8 to 7.8. Nitrite results in the formation of methemogiobin in the blood and results in respiratory compro­ mise. Affected 'fish display signs of oxygen deprivation and may die of asphyxiation.

Quite a lot of CO2 is found in natural water. After it enters water, a small percentage is Nitrate hydrated into carbonic . Some of this Nitrate is the last compound in the nitrogen carbonic acid dissociates into carbonate and cycle and is non-toxic to fish. High levels may bicarbonate ions which are the primary buffers result in excessive algae growth. Regular water found in . Aquatic utilize CO2 changes will help control nitrate levels if for photosynthesis. In the marine environment, problems arise.

CO2 can precipitate as calcium carbonate and become incorporated into the shells and Alkalinity and Hardness exoskeletons of marine . Many aquariums tend to be eutrophic (high in Alkalinity can be defined as equivalent plant ) and therefore unbalanced since calcium carbonate and expresses buffering

CO2 production exceeds reduction and precipita­ capacity. This holds true for fresh as well as salt tion. This results in poor buffering capacity and water, but in the marine environment, about 5%

-). an acid environment. Tanks which contain many of the total alkalinity is due to borate (H 2B04 aquatic plants may require addition of a buffer This buffering capacity is primarily dependent on such as calcium carbonate. the anions (bicarbonate and carbonate) and not on the cations (calcium and magnesium). Nitrogen Hardness represents the total concentration of all cations in fresh water and is usually Most of the nitrogen entering a tank comes expressed in mg/L calcium carbonate. Calcium in the form of ammonia which is excreted by fish and magnesium are the major cations associated directly into the water. Nitrogen cycling in most with the carbonates. Soft water (0-60 mg/L) aquaria is performed by two genera of nitrifying generally has poor buffering capacity while hard . These bacteria and the they water (>180 mg/L) generally has good buffering adhere to is termed the biological filter or capacity. Alkalinity measures buffering capacity biofilter. The nitrogen compounds which are while hardness measures dissolved cations, dissolved in aquarium water are ammonia, which is usually an accurate but indirect mea­ nitrite, and nitrate. surement of buffering capacity.

Vol 55, No.1 11 Salinity and Chlorinity Biological are the best and most efficient "Sea salt" contains traces of many elements, mea.ns of removing ammonia. The natural but six elements comprise over 990/0 of the sea process of is utilized in biological salt,3 These six elements are , magne­ filters in a two step process involving bacteria. sium, sodium, calcium, potassium, and . oxidizes ammonia to nitrate and water tends to be well mixed and rather oxidizes nitrite to nitrate. It takes stable in terms of salinity and elemental several weeks for a healthy filter to develop and concentrations. Chlorinity is the amount of begin functioning adequately. Loading a tank chloride ion (plus bromine and iodine) dissolved with fisl1 before the filter is established will result in one kilogram of sea water. in "New Tank Syndrome".5 Starting a tank with a few and then gradually adding more Introduced Toxic Compounds fish over time will prevent this problem.

Sources of tank water should be included Mechanical when evaluating tank problems. The addition of Mechanical filters essentially strains particu­ chlorine to rnunicipal water supplies is a lates from the water. These filters will usually common sterilization method used in drinking not remove particles smaller than three microns, water. While harmless to humans, chlorine can such as ammonia ions. Out-of- tank power be deadly to . Removal of chlorine filters, filters, diatom filters, and in-tank box can be done with an aerator ("bubbled" out) or filters all employ mechanical . Most by simply letting the water stand over a period of good aquarium systems combine biological and several days. Chlorine can be removed instantly mechanical 'filtration. by the addition of commercially available compounds. These compounds employ sodium Chemical thiosulfate which inactivates the chlorine through Activated charcoal is the primary means of a chemical reaction involving NaCI formation. 3 chemical filtration. Activated charcoal binds Another compound used in municipal water organic compounds efficiently and acts as a supplies is chloramine, which combines chlorine substitute for a biological filter. It is commonly with ammonia, both harmful to fish health. combined with mechanical filtration and enables Bubbling the water or letting it stand will not the system to remove ammonia and other remove chloramine. The water needs to be organic compounds that mechanical filters alone treated with a dechlorinator like sodium thiosul­ cannot remove. fate. Copper sulfate may occasionally be added to Temperature Control municipal water to help control algal growth. Levels over 0.15 ppm are dangerous to freshwa­ Temperature is the easiest parameter to ter fish and levels over 0.2 ppm can be harmful control, yet it is most commonly overlooked by to marine fish. Copper test kits are readily the beginning . Most tropical fish require available in aquarium stores. High copper consistently warm water. Freshwater fish do concentrations require a special type of filter for best between 75° and 80° F, while marine fish removal since there is no acceptable way to prefer slightly warmer . A good remove copper from water without doing water temperature range to shoot for is 77° to 78° F. changes with clean, uncontaminated water. 3 Tank Loading Filtration The number of fish that can be put in a tank A filter removes harmful components from varies with the size of the ta.nk and the 'filtration the water. Successful aquarium systems will system employed. General guidelines are as have at least one type of 'filter and many of the follows: three inches of fish per gallon in fresh better tank systems are equipped with two or water and one inch of fish per three gallons of more types of filters. There are three major water in marine tanks.3 types of filters: biological, mechanical and chemical.

12 Iowa State University Veterinarian Diagnostic Techniques slide.? Wet-mount ilTlpression smears can be made by placing a coverslip directly on the Diagnostic procedures in fish should be lesion. Small 'fin biopsies can be taken using iris carried out rapidly. Fish should be handled scissors and making a wet-mount squash while wearing latex gloves to prevent damage to preparation between a coverslip and slide. the protective mucus layer. Most diagnostic Gill biopsies can be taken by lifting the tests require that the fish be anesthetized to operculum and excising a small portion of the prevent and injury. Cytologic examina­ free border of the gill row. A wet-mount squash tion of scrapings and biopsies taken from preparation can be made, or the biopsy can be external surfaces and gills of fish are the placed in 10% buffered formalin for histologic simplest and most valuable diagnostic proce­ examination. The wet-mounts should be dures. Hematologic evaluation and bacterial examined immediately, as protozoan parasites and fungal cultures can also be useful diagnos­ die quickly and are much easier to identify while tic tools in fish medicine. alive.? Clinical cytologic examinations can be performed on a wide variety of specimens Hematologic Examination obtained from fish. A variety of cytologic stains are available and can be used for fish samples The routine tests used in hematology include without modification. Wright's, Giemsa, new erythrocyte, leukocyte and thrombocyte evalua­ methylene blue, hematoxylin-eosin, phenol tion. In general, the PCV of fish is lower than cotton blue, Gram stain, acid-fast stain, and that of mammals and birds. The baseline modi'fied quick Wright's stain are useful. Rapid values may be less than 20% for some species. stains (Diff-Quik and Hemacolor) also provide fish with values greater than 45% are usually good staining quality.6 considered hemoconcentrated. Stained blood smears can be used to identify hemoparasitism, Skin and Gill Scrapings and Biopsies estimate WBC counts and to study RBC and WBC morphology. Fish frequently suffer from disease conditions A syringe is recommended for blood with lesions involving the integument. A collection because fish blood coagulates rapidly common response of the skin is hyperactivity of when in contact with a surface. Heparin epithelium and goblet cells. This results in a and EDTA are both suitable for coating the thickening of the epithelium or increased mucus syringe and needle to serve as an anticoagulant.6 production that can give a cloudy appearance to Fish should be anesthetized for blood collection the skin. Since the epidermis is not vascularized, procedures. The preferred venipuncture site is there can be extensive epidermal damage the caudal vein lying ventral to the base of the without bleeding.6 tail. The vein can be approached by inserl:ing a Most fish are covered by scales. The needle on the ventral midline of the tail down to skin is composed of noncornified, stratified the vertebrae or laterally a few scales below the squamous epithelium. Cytologic specimens lateral line and directed just caudal to the often reveal a variable number of squamous vertebrae.7 epithelial cells and debris from scales with In small fish, blood sampling is often a occasional goblet cells. Ulcerative lesions sacrificial procedure. After anesthetizing the fish, involving the skin often expose the underlying the body cavity is opened. A needle is inserted dermis and spindle-shaped fibroblasts may be in to the exposed heart and blood is aspirated. seen.6 Cytologic examination of a lesion also An alternative method, with tl1e disadvantage of provides the opportunity to observe parasitic increasing the contamination of the sample, is to organisms directly. sever the caudal peduncle while holding the fish Skin scrapings in 'fish should be performed on tail over a microhematocrit tube. In fish too small anesthetized fish. The edge of a beveled glass to be bled by conventional means, lamellar coverslip or edge of a slide is used to gently biopsy of the gill can be used.6 scrape the surtace of the 'fish in the direction of its scales, avoiding removal of a large number of of Fish scales or injury to the fish. A wet-mount prepara­ tion is prepared by placing a drop of aquarium In most cases, veterinarians face the water on the cover slip and mounting on a glass dilemma of suggesting a treatment without

Vol 55, No.1 13 having first made a de'finitive diagnosis. In light not affect marine fish. They are typically of this, familiarity with the disease problems superficial, cottony growths on the skin and gills most frequently affecting fish can be useful. For that grow in a radially symmetrical pattern. The prevention of many diseases, a quarantine mycelia trap debris so that the lesions may period of three weeks in an aquarium with a eventually lose their white coloration. The biologically activated filter is recommended presence of broad aseptate hyphae are diagnos­ before adding 'fish to an establisl1ed aquarium.5 tic. Since all fungal infections are treated similarly, further identification is not necessary.6 Bacterial Diseases Ichthyophonus hoferi is an obligate internal fungal parasite that primarily affects marine fish. One of the principal causes of aquarium fish Ingestion of infected viscera from feed prepared mortality is bacterial disease. Most of the from infected fish or infected tankmates is bacteria affecting fish are gram-negative probably an important means of transrnission. A aerobes or facultative anaerobes. Potentially granulomatous disease is produced which is pathogenic bacteria are present in the fish's clinically similar to mycobacteriosis. Squash environment as well as in and on the fish itself. preparations of infected lesions reveal the thick­ The total number of bacteria per mL of aquarium walled "resting spores" which are variable in size ...... ,...... r\4 ...... ,.J .. r\R ...... :...... R ...... " I"lr\r\ ...... : ...... " ...... " ... " ...,.. : ..... ,.J: ...... +"II" VVClLCI lJCl11 UC UCLVVCCII I v ClIIU IV VI ~ClIII~III~. utJ LV e:..vv 111I1J1 VIIICLCI ~ II I UIClIIICLCI • Bacterial blooms which are noted as cloudy water require approximately 107 organisms per Parasitic Infections mL. Such blooms can be associated with overfeeding. Many species of ectoparasites and endo­ The presence of bacteria on the fish or in the parasites can infect 'fish and may cause high water is never equated with disease or imminent mortality rates. Fish may have protozoan, potential disease.5 Fish succumb to bacterial metazoan, and crustacean parasites, which are infections after they have been exposed to a readily identified microscopically. Fish may carry stress such as parasitic infections, poor nutrition, a parasite or a population of a few classes of poor water quality, shipping, and temperature parasites without apparent signs of disease. extremes. Bacterial pathogens commonly found Many carriers are mature 'fish that may have in tropical fish are Aeromonas hydrophilia developed a degree of irnmunity to a particular complex, Flexibacter spp., Vibrio spp., Strepto­ parasite.6 When introduced into a group of coccus spp., and Mycobacterrium ssp. uninfected fish, the carrier will initiate an Bacteria can be transmitted orally and epidemic within the aquarium without showing through skin abrasions or damaged gills. Clinical any signs of disease themselves. signs of bacterial infections are similar. Diagno­ Many parasites affecting fish can be sis of most bacterial infections is based on transmitted by direct extension through the culture and isolation of the causative organisms water. Live foods can introduce disease­ in a lesion. Mycobacterial infections are diag­ producing organisms to the tank. Many fish nosed by microscopic examination of acid-fast parasites require an intermediate host which organisms in tissue smears.6 Mycobacterial may be present in the aquarium. Environmental infections have zoonotic potential and may result factors can enhance the clinical severity of in "aquarium 'finger" or "tropical fish finger" in parasitism, including crowding, water quality humans. changes, and nutrition.

Fungal Infections Viral and Neoplastic Diseases

Generally considered opportunistic patho­ Lymphocystis disease is caused by a DNA­ gens, fungi are frequently secondary invaders of containing iridovirus. The virus infects dermal wounds and often colonize dead fish. They fibroblasts and induces them to undergo extreme invariably follow injuries, parasitic infestations or hypertrophy.? Infection results in proliferative bacterial infections.2 Water molds are ubiqui­ nodular growths on the skin that vary in size tous and can commonly be isolated 'from water from pinhead-size nodules to extensive prolif­ and sediments.6 erative masses covering large portions of the Saprolegnia and related genera are the most body.6 The disease may be self limiting,3 or fish common fungi affecting freshwater fish. They do may die of generalized, diffuse skin involve-

14 Iowa State University Veterinarian ment. There is no treatment for Iymphocystis concentration. It can be administered as a bath disease. Surgical removal of lesions may be or in a recirculation system. Sedation is beneficial. In the wild, 'fish are thought to obtained using 15 to 30 mg/L.6 spontaneously recover from the disease. Lymphocystis is more likely to develop if fish are Alka-Seltzer stressed. An Alka-Seltzer tablet dissolved in a small Compared to infectious diseases, neoplasia amount of water is an effective but stressful is uncommon in fish. Tumors of various origins anesthetic. 8 Its use is not recommended. have been documented.6 Fish tumors rarely metastasize. Damage is typically due to local Euthanasia in Fish injury from tissue invasion or pressure necrosis. Ulcerated lesions may become secondarily .Euthanasia in fish is typically through infected. Treatment for neoplasia in fish is overdose of an anesthetic agent. MS-222 at a excision. concentration of 150 to 500 mg/L will humanely kill most species of fish. 3,6 Large fish can be in Fish lifted out of the water and administered concen­ trated anesthetic solution by using a syringe to Fish should be anesthetized during any pour the solution directly onto the gills. Other procedure that is stressful or likely to cause . methods that have been used include decapita­ The majority of anesthetics are administered in tion and intraperitoneal administration of water through the gills. They may also be given pentobarbitone or other anesthetic.6 intramuscularly, intraperitoneally, and orally. A general requirement for all methods of anesthe­ Fish Chemotherapeutics sia is withholding food for 24 hours to prevent complications of regurgitation.6 Drugs can be administered to fish orally The most common method of anesthetic (PO), intramuscularly (1M), intraperitoneally (IP), administration is direct ilTlmersion of the fish. intravenously (IV), or topically in baths or dips. The fish is placed in an aerated container of Topical administration is the most commonly water from its own aquarium with the anesthetic used method. Dosages are based on aquarium in solution and monitored for changes in volume rather than fish . To calculate swimming behavior. The fish may be removed the volume of an aquarium, multiply the depth of when the desired depth of anesthesia is ob­ the water by the width and length of the tained. Recovery is accomplished by placing the aquarium in inches and divide by 231. 5 This will fish in a second aerated container of 'fresh water give volume in gallons. There are three basic from its own aquarium. forms of topical administration of drugs: local­ ized topical administration, short and long­ Anesthetic Agents duration baths and dips, and tank treatments.

Tricaine Methanesulfonate (MS-222, Finquel) Tank treatments MS-222 is the only anesthetic agent licensed Probably the most 'frequently used method of for use in food fish by the FDA. Dosages treating small fish, with the major advantage required to produce sedation in fish vary 'from being ease of administration. However, species to species. As a general guide, achieving safe but therapeutic levels of most sedation occurs at 20 to 50 mg/L, and surgical drugs is difficult. Drugs tend to bind substrates anesthesia at 50 to 100 mg/L, to effect. Induc­ and organic debris in the tank. Biofilters, plants, tion occurs within three minutes. Most fish will and inhabitants can be severely recover uneventfully in 10 to 15 minutes after affected by some drugs. being placed in clean, fresh water. MS-222 also works on .3 Long and short duration baths and dips These treatments require handling the fish Benzocaine but have the advantage of sparing the environ­ Benzocaine is not soluble in water. A stock ment. A separate container is filled with a solution using 10 grams benzocaine in 250 mL known volume of water from the original of acetone gives a concentration of 50 mg/L, aquarium and the drug is added to the neces­ and can then be diluted in water to the desired sary concentration. Dips are generally consid-

Vol 55, No.1 15 ered less than 15 minutes, with baths being References longer exposures. The length of exposure should be based on the time required to reach 1. Pet Supplies 1985 Marketing Survey. Pet chemotherapeutic levels, but is more often Supplies Marketing. July 1985. based on the 'fish's ability to tolerate the treatment.6 Short-duration dips of one second to 2. Scott, PW. Ornamental and the one minute are considered purely topical Veterinary Surgeon. Waltham Third Annual administrations. Symposium: 331. 1981.

Direct topical administration 3. Lewbart, GA. Tropical Fish Diseases, Localized application of antiseptics, antibi­ Therapeutics, and Diagnostic Principles. otic, steroids, or dressings can be very benefi­ AquaMedManual, AquaMed'91. Texas cial. The most common use of this application A&M University at Galveston. June 3-14, 1991. is to cauterize or disinfect a lesion by "painting" with a cotton swab. The fish should then be 4. Ralston, TL. Management of Tropical Fish. rinsed in a water. Severe tissue necrosis and Vet. Technician: Vol 8, No 9. Oct. 1987. burns can be caused by leaving the topical .L .L .L : __ 1 .L __ 1 ~ ~ • __-1 nl\ JII r'\ .L_1 .:_1-.1, : -I .LI-._ U ~cUIII~IIL II! fJ!d~~ LVV IVIIY. ~ o. rVIU, UIVI. Vllldlll~IILdl r!~IIt\~~fJIIIY d! IU LI!~ Veterinary Profession. Proceedings ofthe 4th Summary Kal Kan Symposium. Oct 11-12, 1980.

Symptoms and signs of infectious diseases 6. Stoskopf, MK ed. Tropical Fish Medicine. in fish should be followed using the same rules Veterinary Clinics ofNorth America, W.B. known for history-taking and diagnostic evalua­ Saunders. Philadelphia, PA. 1988. tion in any species. Poor water quality is the major cause of fish disease and mortality and 7. Citino, SB. Basic ornamental Fish Medicine. should be considered when evaluating any Kirk Current Veterinary X, W.B. aquarium problem. Well conditioned fish in Saunders, Philadelphia, PA. 1990. good, clean oxygenated and temperature regulated water are generally resistant to 8. Whitaker, BR. Basic Concepts Concerning disease. Veterinarians and their staff are in a the Diagnosis, Management, and Treatment of position to provide client education services, Fish Disease. 1991 ESVC Proceedings Manual. increase awareness of common fish diseases, and how to avoid 'fish diseases. It is easier to keep healthy fish than to treat sick fish.

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16 Iowa State University Veterinarian