Symptomatic treatment of common Discus diseases
by Dionigi Maladorno

INTRODUCTION

Many aquarists in the hobby do not have access to the laboratory techniques that would allow a specific diagnosis and a targeted treatment of fish diseases. In most cases, symptoms are discovered during routine tank clean-up or fish feeding, and sometimes this leads to inappropriate use of medications that compound the problem. The following document is intended as a support and orientation tool focused on helping the aquarist with few practical recommendations for a first-line treatment of some commonly found discus diseases. Alternative treatments may be used as well, and in some situations different therapeutic criteria may be required.
 

IMPORTANT BACKGROUND INFORMATION
 
A symptomatic approach to the treatment of diseases means that the medications or the procedures used to attempt to cure the disease are chosen on the basis of the type of behavior and physical appearance of the fish, as opposite to decisions made on the basis of diagnostic tests.

It should be however emphasized that the aquarist may discover that obtaining and using a microscope is much easier than what they originally thought. For example, friends or club members may associate to purchase one, or a complacent student, doctor or veterinarian may be available to provide some help. Several hobbyist-grade books^2,3,4 provide very useful information on the use of this instrument, which may contribute to save a lot of money and fish lives.

An effective empirical treatment of some fish diseases is often possible, but it still requires a good knowledge and understanding of the basics of fish physiology and diseases. For this reason, it is extremely important that the hobbyist reads and understands a good book on this subject. Several excellent choices are available^1,2,3,4,7 and they represent one of the best investments in time and money for the discus keeper.

DISEASE PREVENTION
 
The cornerstone of disease prevention is the creation and maintenance of excellent water conditions. The proper physical parameters of the water for a discus aquarium may be somewhat different on the basis of the type of fish being kept, and on the basis of the area of interest of the aquarist. For example, wild-caught Heckel discus have the reputation to be more sensitive to organic waste than aquarium-raised strains, and they also prefer very warm, peaty, soft and acidic water. On the contrary, discus strains obtained by selective breeding are known to have occasionally spawn in relatively harder water conditions, which is considered just fine for simple keeping, without spawning intentions. As a general recommendation, one of the basic disease prevention measures is to conscientiously follow the aquarium set-up and maintenance schedules contained in most books on South American cichlid care⁵.

These books contain in most cases also recommendations on quarantine procedures that should be followed with newly acquired fish. Quarantine is an extremely important concept since it helps to avoid several serious problems, mainly related to infectious diseases . The following table provides a overview of its benefits:

It should, however, be made very clear that while quarantine procedures greatly reduce the problems associated with the acquisition of new fish, there is no guarantee that the problems will be eliminated completely. Some diseases may have an incubation period so slow, that it takes months before symptoms appear. In other cases, a new fish may simply be an healthy or sub-clinical carrier of an infectious disease. In other words, infection is not always associated with disease. This means that the carrier does not show signs of the infection although a potential pathogen is present, and the quarantine is completed with no problems. However, other fish later on infected by the same agent in the community tank may start to manifest symptoms. This type of situation is for example encountered with Ichthyophthirius multifiliis ("Ich") infestations. It can go even the other way around, with newly introduced (and quarantined) healthy fishes being infected by pre-existing ones whose immune system was able to keep the parasite under control⁴.

The risk of parasite infestation is higher in wild-caught fish than in animals obtained directly from a reputable breeder. Fish purchased from stores may be in good shape, but because of the promiscuity with wild-caught or otherwise sick specimens, they should be considered at high risk of carrying potential pathogens. Some hobbyists do not routinely disinfest the fish coming from known and reliable sources, using the quarantine period just for observation. On the contrary, high risk specimens are often preventively disinfested. A discussion of the pros and cons of these procedures however goes beyond the purposes of this document.

When setting up a quarantine (or hospital) tank, it is important to consider the following recommendations:

1) The filtration system used should be able to cope with the ammonia produced by the fish. In other words, the filter must have been cycled , otherwise a procedure designed to improve the health of the fish becomes more like the execution of a death sentence!

Since relatively few people can continuously maintain a spare tank running, the hobbyist should always have extra filtration material available from other established tanks in order to "seed" the filter of a newly setup quarantine tank. Filter "booster" preparations are commonly available in aquarium stores, and many users report good results with them. Since however controversies exist on exactly which bacteria are responsible for de-nitrification ⁶, in the opinion of the author it is uncertain that the product will contain what really is needed to accelerate the maturation of the filter. The availability of a kit for ammonia and nitrites is also a very useful tool to make sure that there is no accumulation of these toxic compounds before (if previously running filters and or water from other aquaria were used) and after introduction of the fish. The tank should be understocked in order to provide the best possible water quality for the fish.

2) Quarantine tanks are normally bare, with just a few plastic plants and/or plastic driftwood if the fish requires cover to prevent or reduce stress (although the author considers this point very important, and almost a necessity for discus, it is a fact that many experienced discus keepers disagree and achieve excellent results with bare tanks). With or without plastic plants, these tanks are intrinsically more unstable than an established tank, and the importance of daily and adequate water changes is extreme, unless contraindicated by the medication schemes being used. As a general indication, daily 25% water changes should be considered a bare minimum for a mildly understocked tank (for example, two discus in a 30 gal tank). The walls and bottom of the tank should be kept as clean as possible: even apparently minor slime coating of the glass can hide massive amount of microorganisms which are able to dramatically decrease the oxygen content of the water (it happened to the author!!) and give the fish respiratory and neurological problems.

3) A reliable and adequately powered heater with easy-to-adjust temperature settings should be used, and an airpump with airstone may help to maintain the water well-oxygenated.

4) Nets, vacuuming equipment, buckets and any other equipment used in the quarantine tank should not be utilized, as a precaution against transmission of diseases, for any other tank. Procedures for equipment sterilization are explained in the above-mentioned fish health books.

HOW TO BUY MEDICATIONS
 
Medications have an expiration date beyond which they may loose their effectiveness. Light, moisture and elevated temperatures are factors that may dramatically accelerate the rate of degradation of drugs. Unfortunately, many remedies available in aquarium stores do not carry any expiration date, nor are kept under acceptable storage conditions. Warm temperatures, moist environment, display on racks under full light are factors normally affecting the commercial preparations sold in the hobby. Other times it is the hobbyist himself who decides to use old products just to clean up the medicine cabinet!

These situations should be avoided. Here are some useful tips to consider on the subject of purchasing and keeping medications:

1) Unless you are planning to acquire several new fish in a short period of time, or you have a very large number of aquaria, do not buy medications "just in case". Few treatable conditions require an immediate use of medications, and in most cases it is better to start with water changes, temperature adjustments, home remedies like salt or just careful observation. Wait another 24 hours until stores are open and buy a fresh package of the exact drug you need.

2) Buy medications from a store that has a high volume of sales and that keeps them in acceptable conditions. Stay away from dusty or moisture-stained packages. An airtight sealed container is preferable to boxes or bottles that can be easily opened and contaminated.

3) Formulations with an expiration date and a clear label explaining contents and concentrations are much more reliable than those with unknown or poorly described content.

4) Store what you bought in a cool and dry place. If you opened an airtight container, it is unlikely that after a few months the content will still be viable, and you should dispose of it in a safe place.

5) Keep you aquarium medications out of the reach of other pets or children.

SOME PRINCIPLES ON USE OF MEDICATIONS
 
The medications most commonly used to treat diseases in ornamental fishes are antibacterial, antifungal and antiparasitic drugs. It is important that the aquarist understands that each category of pathogens has different types of targets on which these medications work , and that therefore a "magic bullet" does not exist.

Even within the same category of pathogens, say for example bacteria, there are major differences in the susceptibility to each antibiotic, which therefore should be chosen on the basis of a careful selection of the most active compound. The effectiveness of any compound on a given target is an intrinsic characteristic, but it may be influenced by the dose used, by the frequency of administration and by the duration of use. In addition, sometimes adverse effects occur as a result of toxicity occurring not only on the target organism, but also on the host. Sometimes some characteristics of a drug (for example, the ability to diffuse to all body tissues and fluids) are very desirable because they make it more efficacious, but unfortunately this increased efficacy is also related to increased toxicity. This is not however always the case, and the commonly heard statement that "potent" drugs are more toxic is quite misleading. There are in fact some antibiotics that are quite toxic and not effective at all, and others that are very well tolerated and very effective!

On the market several "cocktail" preparations are available, which contain a mix of different drugs which are hoped to cover the desired target. This is sometimes perceived from the aquarist as an excuse for not trying to learn and understand what type of disease is affecting the fish. The use of single preparations that are (erroneously) believed to cover every problem is commonly called the "shotgun" approach! The downside of this idea is that in most situations the majority of the array of chemicals given to the sick fish are useless in terms of efficacy, since they are not targeted on the desired pathogens. This may "mask" the characteristics of the disease and it can cause unnecessary toxicity problems which could have been easily avoided by selecting only the proper compound. In addition, other problems such as avoidable selection of resistant pathogens may occur as well. These cocktail preparations are particularly dangerous when they contain mixed antibiotics active on bacteria, which in most cases achieve the only result of very effectively kill the "good bugs" that degrade ammonia and nitrites in the filter. In addition, bacterial infections are very often secondary to injuries or parasite infestations, and once the primary cause is taken care of, they may resolve with just clean and healthy water conditions.

This is one more reason to use medications with caution and following specific criteria.

DISCLAIMERS

The author does not assume any responsibility on possible negative effects related to the use of the medications and treatment schemes mentioned in this paper. The ultimate decision on what to do is in the hands of the owner of the aquaria, which is encouraged to decide on his actions after having reviewed the available literature and, if necessary, obtained help from qualified professionals. Several ornamental fish magazines carry advertisements of companies providing advice on fish health problems, and many veterinarians may be available to give professional advice. The author has no financial or personal interest in any of the companies marketing the products recommended in this paper.

GENERAL PRACTICAL RULES FOR USE OF MEDICATIONS IN AQUARIUM SETTINGS

In general, before a medication is introduced in the aquarium, it is necessary to:

• Carefully clean the tank, making sure however not to disrupt biological filtration cleaning the filter with excessive enthusiasm! Organic compounds accumulated mainly at the bottom and in the filter may inactivate some medications¹.
• Remove, if present, any activated carbon or other filtration resins. Discontinue the use of any water additive (slime coat protectors, detoxifiers for heavy metals, etc.) that may inactivate the drugs being administered. Inert filtration material such as foam blocks, filter floss, ceramic beads are OK.
• Start keeping a log, which by the way should be kept regardless of disease outbreaks! It will help to remember the correct dates and dosages used.
• If medications that are toxic to snails will be used (not many, if it is the case it will be indicated in the following text), as many snails as possible should be removed, in order to reduce toxicities due to decaying once they die. Manual removal after baiting with lettuce or fish food (in a container with holes large enough for the snails, but not for the fish) is reasonably effective. In extreme cases, a remedy not toxic for snails (or the complete tear-down of the aquarium) should be considered.
• Inactivate the UV sterilizer, if one is being used, since it may make some medications less effective.
• During treatment, feed the fish very lightly, in order not to overload the bacterial filtration in such a critical moment.
• If treatments require the calculation of drug concentrations and volumes/weight of medication to use, ask a friend to review it for possible errors.

• Make good-sized water changes (indicatively 30%) daily for several days.
• Introduce in the filter a bag with activated carbon, in order to remove the medication. Remove the bag after 2-3 days.
• Resume normal water change and feeding procedures after you are sure the nitrification process is working efficiently.
• Observe the fish very carefully for several days, in order to understand if the treatment given had any effect and therefore be able to plan any further action possibly needed.

TREATMENT OF COMMONLY FOUND SYMPTOMS

ABNORMAL FECES AND/OR WEIGHT LOSS

When the fish loses weight there are several explanations that the aquarist should consider³. Weight loss may or may not be associated with abnormal feces or aspecific symptoms such as color darkening, and it is often the only symptom initially noted by the fish keeper. In other cases, an otherwise apparently normal fish produces long, stringy and whitish feces, which are often deemed to be one of the tell-tale signs of infestation with Hexamita or other ciliate protozoans^3,4. From a practical standpoint, either sign, weight loss or abnormal feces, is an indication of possible gastrointestinal problems, and the treatment recommendations that are given in this paper are the same.
 

What follows is just a summary of some of the most common primary causes of this type of problem. For a comprehensive list see the above-mentioned references on fish disease books:
 
 

While to intervene for the third category of causes is very difficult, the first two can be managed successfully if properly recognized. Re-arrangement of the aquarium and of its decor, provision of hide-outs, live foods, feedings targeted to the weaker fish can reduce the causes of hunger strike due to stress. A careful evaluation of the water parameters, followed by water changes and other chemical and physical manipulations is in most cases followed by complete recovery of the fish, unless major organic damage has already occurred.
 
 

Several of these organisms have complex life-cycles which include forms such as eggs or cysts which are not easily attacked by some drugs, which kill only adults. Even if those are killed by a first antibiotic treatment, the surviving resistant forms may mature and continue the infective process. This is a factor which can easily lead to improper use of some antibiotics, which should be used in some cases in repeated cycles in order to definitely interrupt the life-cycle of the pathogen.

Several different types of pathogen may be simultaneously present in a diseased fish, and in the absence of accurate laboratory diagnostic criteria, it is preferable to administer carefully chosen drugs that cover both flukes and tapeworms, possibly nematodes also.

Because of this multiplicity of possible causes, a multiplicity of possible solutions obviously exists! What follows is a type of approach that has been used successfully by the author in case one or more fish in a tank manifest weight loss and/or abnormal feces:

1) EXCLUDE NON-INFECTIVE CAUSES: in case of weight loss alone or with other aspecific symptoms such as color changes, the compatibility of the affected fish with its tankmates should be carefully re-evaluated. In addition, several critical water parameters should be checked immediately (temperature, pH, ammonia, nitrites, nitrates). Even in old and established tanks some unpredictable and undetected event (malfunctioning of a heater or of a filter, unnotified change by the water company of the tapwater chemical parameters, etc.) may occur.

If any abnormality is found, it should be corrected and a period of observation of several days should follow. If no cause of abnormality is found, then:

2) HYPOTHESIZE AN INFECTIVE CAUSE: in such case, the likelihood of generalized infestation of all the fish in the tank is very high, even if only one shows some symptoms. Therefore, to isolate the affected fish in a hospital tank may be done in order to give some rest and protection to a very weakened individual, but this is not strictly a necessity, nor it is a justification for not treating the whole community tank.

A treatment should be chosen in order to interrupt the negative effects on the health of the diseased fish, as well as to break quickly and efficiently the life cycles of the potential pathogens (to prevent infections of new fishes as well as re-infestation of the one originally sick). A simple and generally very effective scheme of treatment is the following:

a) Treat first for flagellate infestation:

• metronidazole, see treatment scheme at the end of this paper. A week later:

Various options exist (choose one only):
• In the direct experience of the author, one of the most practical solutions for occasional use is a product commonly available in the US, named Fluke-Tabs^TM . See treatment scheme at the end of this paper. The following two alternative solutions are however preferable, because the unknown dosage of the individual components of this product does not allow the user to knowingly manage possible toxicity problems.
• Flubendazole. See treatment scheme at the end of this paper. This is the treatment preferred by the Author.
• Praziquantel (Droncit^TM ) is a compound available in the US only through prescription from a veterinarian. See treatment scheme at the end of this paper

 

 
 

The most common eye problems encountered in Discus are, in the opinion of the author, superficial wounds or scratches with subsequent bacterial or fungal superinfection. The eye often appears partially or totally off-white and opaque, and often a cotton-like growth covers it. It is a situation that looks extremely serious but luckily very often it is possible to obtain a complete recovery.

The remedy is very simple:

1) Attempt to understand how the problem occurred: sharp edges of aquarium decor, aggressive tankmates (especially in situations of overcrowding), careless handling during netting attempts are some of the primary causes, which need to be eliminated in order to proven further episodes. In the direct experience of the author, attack from other fishes (including other Discus) is the most frequent culprit, and it should lead to a critical re-evaluation of the fish density and availability of space and shelter for everyone in the tank.
 

2) The traditional home remedy of kitchen (or aquarium) salt is extremely effective, and the frequently recommended antibiotic courses should be considered only as second-line treatment if salt does not work. See the treatment scheme with salt at the end of this paper.

Concerning the other possible eye lesions, several different causes may be at the root of the problem. On a case-by-case basis, a check of the water parameters and a review of the descriptions and explanations given by a book on fish diseases may help to understand the situation. In the absence of a valid explanation, it is better to just focus on maintenance of good water quality, and refrain from using medications temptatively.

LESIONS OF THE FINS

Fin rot is a common problem, due most often to poor water quality or physical damage during transportation and fights with other fishes. Often fungi and bacteria may infect the lesions, producing a whitish edge. In addition to the obvious need to remove the primary cause of the problem, several reference books recommend antibiotic treatments. The Author did not have much success with that, but simple addition of kitchen salt proved to be extremely effective, stimulating complete regeneration of the lost tissue. See the treatment scheme with salt at the end of this paper.

Concerning the first of the remaining two groups of abnormalities, fin clamping is a very aspecific behavior which indicates some form of distress and that should simply alert the aquarist to carefully observe the fish for the presence of other, more specific problems. It may be due to skin parasites, but also to internal diseases. It becomes a real concern when it is a persisting problem, and when it occurs in conjunction with other aspecific symptoms, such as darkening of the skin. A treatment should however be initiated only after a presumptive specific cause for the fin clamping has been identified.

White spots on the fins are basically due to the same group of pathogens that can cause this type of lesions on the skin. See such section for details.
 
 

TREATMENT SCHEMES (FOR PART II)
 
 

REFERENCES (FOR PART I AND II)

1. C. Andrews, A. Exell, N. Carrington (1988). The Manual of Fish Health. Tetra  Press.

2. D. Untergasser (1989). Handbook of Fish Diseases. TFH, Neptune, NJ.

3.  D. Untergasser (1991). Discus Health. TFH, Neptune, NJ.

4.  D. Untergasser (1991). Malattie dei Pesci d’Acquario. Primaris s.a.s., Milano.

5. P.V. Loiselle (1994). The Cichlid Aquarium. 2nd Edition, Tetra Press.

6. T. Hovanec (1997). Nitrifying Bacteria - Part Two. Aquarium Fish Magazine        (January)

7. V. Zupo (1990). Le malattie dei pesci. Ed. Olimpia.

8. Hex-A-Mit^TM, Dose Instructions  (Aquatronics, P.O. Box 6028, Zuma Station,  Malibu, CA 90265,  U.S.A.)

9. Unknown Author (July 1995). Tropical Fish Hobbyist, page 151. TFH, Neptune,  NJ

10. Fluke-Tabs^TM, Dose Instructions (Aquarium Products, Glen Burnie, MD 21061)

ACKNOWLEDGMENTS
Many thanks to Kevin Conlin for the accurate review given to the manuscript and to Raffaele Bufo for the support and the patience he had with such a slow writer like me!
The Author would also like to thank the contributors to the Discus-L list for the information shared among the members.

THIS PAPER OR PARTS OF IT CAN NOT BE REPRODUCED WITHOUT PERMISSION OF THE AUTHOR
  Symptomatic treatment of common Discus diseases - I