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Related FAQs: FW Troubleshooting, Freshwater Disease, Freshwater Disease 2, Freshwater Disease 3, FW Disease 4, FW Disease 5, FW Disease 6, & Toxic Situations, Infectious FAQs, Parasitic FAQs Ich/White Spot Disease, Worm Diseases, Freshwater MedicationsNutritional Disease, Goldfish DiseaseAfrican Cichlid Disease 1, Cichlid Disease

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Solution Chart for Freshwater Diseases 


Bob Fenner


 Disease, by definition, is any deviation from a normal or healthy condition. As such diseases can be categorized a few ways by their root causes, appearances, and likely treatments. Here I will try to illustrate the most common ailments of captive freshwater organisms, particularly fishes, their symptomology, causes, and best proven means of remedy.  

Environmental Diseases: The Single Largest Source of Captive Aquatic Morbidity & Mortality

            Poor water quality is the absolutely largest source of disease in freshwater livestock, likely directly and indirectly accounting for ninety some percent of losses. If only aquarists would set-up their systems properly, be patient re establishing complete biological cycling, be conscientious re stocking, feeding, maintenance morbidity and mortality of aquarium organisms would be greatly diminished. Categorizing these many types of mal-influences can be done in a few ways, but their symptomology and treatment is closely related: Poor behavior, rapid to slow labored breathing, setting on the bottom, floating disoriented near the surface lack of awareness and response to your presence. The real cure? Discovering the root cause/s and alleviating them.

            As a general rule, the first and foremost thing a hobbyist can and should do in discovering such anomalous behavior in their livestock is to 1) test their water for what they can temperature, aspects of nitrogenous poisoning, pH and even if all checks out for what they have tests for, 2) Execute a good (25%) water change, with tap-treated water possibly adding chemical filtrant/s (e.g. activated carbon) to the filter/circulation flow path, or even moving the mal-affected livestock (if possible) to a more promising setting.

            Ammonia/Nitrite and Nitrate Poisoning: The all-time greatest killer of aquatic livestock has been, is and likely will be metabolite poisoning. This is mainly due to waste products accumulating and not being cycled expediently. Why? From hobbyists not being patient enough, providing for their system to cycle completely, and killing off their beneficial microbes through the use of medicines, over-feeding, over-crowding and other influences. Test kits are an absolute necessity (your own) at these times, as is careful catching of the problem from close observation, and quick action to remove the toxic chemicals through water change-out dilution, addition of useful bacteria products and/or seeded media, or removing the life to another cycled setting.

Low Oxygen, High Carbon Dioxide: Shows up quite often in home settings, from the collection of dust, aerosols and cooking oils settling on the tanks air-water interface. Such accumulations can be deadly, at times quickly leading to fish gasping at the surface. Solving them is easy enough, by dipping a clean pitcher edge-wise in the tank, or wicking the material off with a plain paper towel. Of course, vacuuming a bit of the water off the surface during regular water changes is a good idea as well.

            High Temperature Stress: can occur from hot weather or a malfunctioning/mis-set heater. This looks a lot like the gaseous exchange problem above in its symptoms. Fixing the water temperature (slowly) by changing water out, turning the light off, taking the top off (while lowering the water level to prevent jumping) all help in the short term. Obviously, the less-crowded, better maintained, filtered, and aerated your systems are the less likely a temperature spike is likely to mal-affect your livestock.

            Other General Poor Water Conditions:  include such issues as the presence of chlorine/chloramine sanitizer, too high or low or vacillating pH, hardness, metal poisoning, noxious algae poisoning, addition of too much salt Again, these situations are best avoided by understanding what you need to know per your given livestocks needs and tolerances and your set-up, and being diligent re maintenance and feeding. Do pre-treat, and store change-out water a week or more ahead of use. This allows for variations in its supplied quality, the removal of sanitizers (chlorine, chloramine) and you to adjust other water parameters way in advance of its actual use.

            Injuries/Physical Traumas: A surprising number of fishes are damaged from netting, jumping or running into aquarium walls, décor items Much of this can be avoided by providing adequately large systems, with space to move about, and being careful to provide some outside lighting before and after turning the aquarium lighting on and off.


Social Diseases: Crowding & Aggression:  Too often discounted as a contributing cause of freshwater disease, the ill-effects of crowding, placing improper numbers, sex-ratios of aquatic animals can easily lead to their loss. Again, investigate before you buy livestock. Know its needs for room behavioral, psychological and growth characteristics, likely compatibility Is it a social species? How many make a good school for it? Should there be more than one male present? How many females, or is this important?

            The most important tool you can have as a hobbyist is your close powers of observation. Simple chasing, the occasional fin nipping are likely not problematical. Continuous chasing, driving of some animals by others into hiding, non-feeding is critically important. Your system is just this: a system with you as grand arbiter. Be ready to act if there are signs of overt aggression, incompatibility in this world of your design.


Bacteria, Funguses: Infectious Pathogens:

            Fungal/Mold Infections: These appear as white to colorful cottony growths on the body of affected fishes. These are opportunistic organisms that take advantage of damaged fish life in compromised environments. Keep your systems clean, your livestock healthy, and you wont have trouble with fungus infections. Advanced cases can be treated with Malachite Green solutions, with the warning as stated below.

            Bacterial Infections: There are a few key genera/types of bacterial involvements that can cause real trouble in FW systems, mainly ones that are too dirty, poorly maintained, or that have had a very sick organism transferred/placed in them that has a hyper-infective state going. Aeromonad Infections (Aeromonas) are typically evidenced as non-emarginated red sore areas. Culture of the causative organism is necessary to determine which antibiotic may be efficacious. Columnaris (Flexibacter) looks a lot like a fungus with common names like Fin Rot, Cotton Wool Disease. Close inspection will show ulceration, reddening and necrosis of the skin and gills, especially prevalent in livebearers and Gouramis as a whitish band about the caudal peduncle accompanied by lying at the bottom and shimmying. This problem must be identified and addressed rapidly. Neomycin Sulfate will often stop it, though commercial businesses avail themselves of potassium permanganate and copper solutions. Mycobacteriosis/Fish TB (Mycobacteria) is sometimes seen in non-feeding, emaciation, as open sores, particularly in Anabantoids and Minnow fishes other times as simple morbidity/lethargy or un-marked deaths. No given antibiotic has proven to be effective in all cases.

            Viruses: Lymphocystis: Is a gray to white nodular-cauliflower like growth that occurs mainly on fish fins it can be of little mortal consequence but is unappealing in its appearance. With improved water conditions, nutrition it will often disappear.  


Protozoan Infestations:         

            Ich(thyophthirius), Whitespot Disease:  What youre actually seeing here is not the disease itself (the ciliates are microscopic) but the reaction sites of the irritated fish host its body mucus expressing itself at the areas of irritation. This insidious single-celled animal can rest up in most all freshwater systems, waiting for weakened conditions of host fish/es to reproduce itself into plague numbers. Avoiding undue stress and outright introduction of hyperinfective states (by careful livestock selection and quarantine) is important. For many species, simply raising the system temperature to the mid to upper 80s F. will effect a cure (if the host fish/es are not too debilitated). For others, treatment with an ich medicine (generally consisting of Malachite Green, possibly Copper, maybe with Formalin) is efficacious Do be aware however that many scale-less and small fishes (e.g. Catfishes, small Tetras, Knifefishes, Mormyrids) are sensitive to these medicines and should be carefully dosed in half the stated dosage.

            Velvet: is caused by a Dinoflagellate Algae, and appears as its name implies as a light dusting or coating on the side of its parasitized host fishes. Most often occurring on Gouramis and their relatives, Killifishes and livebearing toothed carps, Velvet can occur on most all freshwater fishes. Salt immersion (where the species involved can tolerate this), copper-based medication (careful in soft, acidic water) can effect a cure. Allowing infested systems to go fallow (w/o fish hosts) for two weeks kills off resident populations through starvation.

            Hexamita (Spironucleus): Well mention here as its often identified as a/the causative organism of Head & Lateral Line or Hole in the Head Disease. I am of the opinion that this syndrome (HLLE, HTH) is more caused by nutritional deficiency and poor water quality issues, but Hexamita itself is an important/deadly protozoan disease (particularly of Cichlids and Anabantids), causing massive mortalities at times (particularly in Angels and the genera Colisa and Trichogaster Gouramis). Microscopic examination of feces or necropsy of the lumen are definitive Treatment with Metronidazole/Flagyl has proven effective.  


Worms Disease of All Sorts: Internal & External:

            Leeches: Are largish (generally a half inch or more in length) parasitic relatives of earthworms They have two body suckers to attach to fish hosts, and are generally blackish in color. Happily these animals have direct life cycles and are best removed by simply extracting any adult forms found. Alternatively organophosphate/s may be used (carefully) as per treatment for FW crustacean parasites to rid a system of Leeches.

Gill and Body Flukes: most often occur in dirty water conditions, as whitish body markings/blotches, eroded finnage and general malaise of the infested fishes. These are microscopic worms that cannot be seen directly w/o the use of a microscope, but can be treated for with either an organophosphate or purposeful de-wormer (e.g. Praziquantel, Mebendazole).

            Crustacean Parasites: of freshwater fishes are mainly represented by the Fish Louse (Argulus) and Anchor Worm (Lernea). As adults these appear as external parasites looking like a semi-transparent half small thumbnail with twin trailing egg sacs in the case of Argulus, to just exposed longer (1/8-1/4) body segment (head embedded under the skin, scales) with twin egg sacs in Lernea. Infested fishes show declining degrees of lethargy. Adults should be removed by careful pulling using tweezers, and the system treated with an organophosphate (likely DTHP/Masoten, or Dimilin variously sold, incorporated in Fluke Tabs, Clout and other commercial products) to remove non-mature forms. These crustaceans are mainly seen in pond-raised goldfish, but can occur in tropicals raised in such settings as well.


Nutritional Deficiencies: These syndromes show as eye and body deformities, a lack of feeding. Their remedy is to discard old (more than three months at ambient temperature)/contaminated/deficient foods and replace with ones of complete nutritional value. Be aware that not all fishes eat flakes and that the protein content for non-predatory species (the best examples, goldfish, minnow-sharks) should not be too high (no more than 20%) as these fishes dont consume or process such foods in the wild.  


Re: Treatments In General/Specifics: It cannot be emphasized strongly enough that you must read a manufacturer of treatments packaging thoroughly and follow it to the letter. Most of the time chemical filtrants need to be removed, water quality must be monitored carefully, and feeding kept to a minimum Dosages are stated per ACTUAL gallonage you should measure yours accurately discounting displacement for anything other than water and stick to the stated methodology exactly. Allowing chemical concentrations to be too low/high can be disastrous, as well as not treating for the stated length, re-treatment interval.  

Conclusion: As you can see/appreciate there are several interacting components that determine health/disease. Knowing how to identify and pick out healthy specimens, isolating them for observation and rest, supplying them with an appropriate environment and nutrition, and excluding disease-causing organisms is the gist of tilting this balance to health of your livestock.

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