Effective Fish Disease Treatment and Prevention

The first step in the successful treatment of diseases in aquarium fishes is early recognition and proper diagnosis.

Even before a disease condition can be diagnosed it must be recognized as existing. Since the fishes cannot simply tell us that they are feeling uncomfortable we must educate ourselves as to their normal and abnormal behaviors so that we can have a functioning ‘early warning system‘.

A male cichlid that is observed glancing off of rocks and other stationary objects in his aquarium may be showing signs of an early parasitic infestation, or he may just be advertising his territory to other fishes in his tank. A wrasse that is found lying on its side at the bottom of the tank may be in respiratory distress and dying, or it may simply be resting.

Before dumping in Dr. John’s Miracle Tonic one must first ascertain if the problem is simply a behavioral quirk that is being manifested, or if there is a real problem that needs the aquarist’s attention.

If one is certain that a problem exists the next step is to determine if the problem is related to environmental conditions or to biological causes.

Typical environmental problems are:

Treatment For high Ammonia Levels

For high total ammonia levels one needs to be most concerned if the pH is significantly above 7.0 and if so, if the total ammonia level is above 0.5 mg/L (if as NH3, or above 0.4 mg/L if as ammonia-nitrogen, NH3-N).

Water changes with totally ammonia-free water is a viable treatment for this problem, but since most domestic water supplies in North America contain ammonia (usually in the form of chloramines, NHCl2 and/or NH2Cl) treatment with AmQuel is the usual course of action in either freshwater or saltwater aquariums.

Treatment for Excess Nitrite in Aquarium

High nitrite levels (above 0.3 mg/L as the nitrite ion, or 0.1 mg/L as nitrite-nitrogen, NO2–N) are really only a concern in freshwater aquariums.

In marine aquariums the plethora of chloride ions, Cl-, overwhelms the nitrite ions, NO2-, and prevents any significant toxic effects to the fishes. In freshwater aquariums a partial or complete water change with nitrite-free water is the best action (most domestic water supplies are free of nitrite contamination, but a quick test to verify this is always in order).

In combination with the water change is the addition of chloride ions, usually as sodium chloride (ordinary table salt), at a concentration of about 30 times the nitrite concentration. It is usually safe to add an excess of salt to the water and to eventually dilute it out of the system with regular partial water changes once the crisis is past.

A dosage of 500 mg/L of salt (either iodized or non-iodized) will be sufficient to counteract the effects of 10 mg/L nitrite (as the ion). This dosage equates to about 1 teaspoon (approximately 6 grams) of salt to each 3 gallons of water in the aquarium.

Treating Low Oxygen in Aquarium

Low dissolved oxygen is most easily corrected by an immediate partial water change and a significant increase in the aeration of the water.

Remember that aeration means gas exchange and that such exchange only takes place at the water’s surface. Very little oxygen enters the water from bubbles, but agitation of the surface by bubbles causes the maximization of the dissolved oxygen levels.

Any water surface disturbance increases aeration.

The usually signs of oxygen starvation are not observed; instead, dead fishes are found. This is because during the hours that the aquarium is dark is the time that the greatest low-oxygen stress is likely to occur.

When in the dark the live plants (including algae) in the tank consume dissolved oxygen and lower its concentration in the water. At the point of lowest concentration the fishes will quickly suffocate. Low dissolved oxygen levels are always a concern in aquariums filtered with reverse-flow undergravel filters and with little or no auxiliary aeration.

Other water quality parameters such as nitrates, phosphates, alkalinity (erroneously called “carbonate hardness”), salinity and hardness are of little concern. This is due, primarily, to the fact that these parameters either aren’t toxic, even at high concentrations (nitrates and phosphates), or don’t change rapidly enough to suddenly cause stress in the aquarium’s inhabitants. The one consideration not mentioned is pH.

Treating for Sudden Ph Changes

Sudden pH changes can be quite deadly to some fishes. This is often due, however, to concurrent changes in the toxicity of:

  • Ammonia (which is more toxic at higher pH)
  • Nitrite (which is more toxic at low pH) or
  • Carbon dioxide (which is also more toxic at low pH and which interferes with normal respiration).

Just changing the pH will not usually result in death. It may result in stress however, and for this reason pH changes of more than 0.3 pH points should be avoided unless experience shows that such a change is of no concern.

Treating for Other Toxic Substances

Toxic substances that may be present in the water supply can sometimes be the cause of stress and death. If such substances are suspected their presence must be determined.

If copper is present in the water supply at a concentration above 0.5 mg/L then treating the water with NovAqua to precipitate the copper is the best action. Aeration and pH adjustments will do little or nothing to remove the copper.

Likewise, chlorine, chloramines and ammonia must always be removed from the water supply before using it for the aquarium.

NovAqua will remove chlorine and it will break the chlorine-nitrogen bond in the chloramines and neutralize the freed chlorine.

AmQuel will react with and remove ammonia from water supplies and it will also dechlorinate (although in a different manner from NovAqua).

Using both products together for new water is always the best choice. NovAqua, of course, helps buffer the new water to a more suitable pH, and it adds physiologically active electrolytes that may be missing from tap water and which fishes require to help mitigate stress, and it provides a tertiary, synthetic skin slime replacer to fishes that may temporarily require it.

Effective Treatment For Fish

Once environmental conditions are remedied and/or eliminated as the possible cause of disease then the aquarist is faced with properly diagnosing an ‘organic’ disease condition and treating it. To reiterate, early diagnosis is a must.

Hand in hand with an early, and proper, diagnosis is application of an effective disease treatment. There are several things inherent in the concept of “effective fish disease treatment”. Among these are:

  1. Removal of the diseased fishes to a separate quarantine and treatment tank (Q/T tank)
  2. Significant water change and cleaning or replacement of the mechanical filter medium and replacement of the granular activated carbon in the outside power filter of the main tank
  3. A partial water change in the Q/T tank just prior to any application of drugs or medications.
  4. Selection of the proper treatment method
  5. Continuing the treatment long enough to insure against a re-occurrence.

Isolating infected fishes

Isolation of the afflicted fishes in a Q/T tank should not be in question. The inability to remove diseased fishes from their main aquarium will make the job of successful treatment difficult if not impossible (especially if organisms that will react negatively to the treatment regime are present).

A suitable Q/T should be available at all times; such a tank can be set-up and maintained just like any other aquarium, but it should stand ready to receive new arrivals for the purpose of quarantine, and to receive diseased fishes from the main aquarium(s) should the need arise.

To keep biological filtration active in a Q/T tank a small population of hardy fishes (danios in freshwater and mollies in saltwater) can be kept as more or less permanent residents. Removing such fishes prior to introducing any diseased fishes should be considered.

Changing aquarium water

Performing a water change on the main tank serves at least two purposes. If done just before removing the diseased fishes the smaller volume of water often makes it easier to capture them.

Removing water from the main tank means removing a portion of free-swimming disease-causing organisms (if present) thereby lessening the chances of otherwise unaffected fishes of acquiring the disease. Adding the new water refreshes the remaining water with dissolved oxygen. The effects of replacing and cleaning the filter media in the outside power filter should be obvious.

At this point it needs to be pointed out that any significant cleaning of the gravel bed in a functioning undergravel filter may be contrary to what is needed at the time. This is because a vigorous cleaning of the gravel might result in the removal of a significant population of the beneficial nitrifying bacteria.

It is often thought that the mulm that accumulates in old gravel beds is somehow detrimental. In fact, this material is populated by beneficial bacteria and it probably represents the end product of bacterial decomposition of wastes in the aquarium rather than a potential reservoir for such decomposition.

At any rate, soluble metabolites do not accumulate in the gravel; instead, as with all soluble substances in the aquarium, they are evenly distributed throughout the water column.

A partial water change in the Q/T tank prior to the addition of any drugs or chemicals to the water is for the same purposes as stated above. Partial water changes must be made before each retreatment, too.

After the first treatment each subsequent partial water changes removes additional disease-causing organisms present in the water as well as a portion of the medication that may have partially or wholly decomposed or become inactivated. Water changes during the course of treatment are necessary even if it is stated as being unnecessary on a given treatment’s label. Water changes will help insure against the build-up of toxic substances (e.g. ammonia and nitrites) as a result of inhibition to the normal biological filtration.

Another warning, or reminder, is in order here; the therapeutic dosages of many medications is often very close to their toxic dosages. That is, effective medications are often stressful to the fishes, the hosts, as well as inimical to the disease. Therefore, addition of a given medication to an aquarium may be the proverbial straw that breaks the camel’s back. That is, the disease may have progressed far enough so that even with the very best possible choice of treatments the treatment itself may cause the death of the disease fishes. Many medications have similar effects upon the hosts as they do the disease-causing organisms (pathogens); the reason the hosts usually survive the treatment and the pathogens do not is often related to size and differences in physiological processes that allow exposure of the medications to the cells of the hosts and pathogens Some treatments (e.g. copper) may actually stress otherwise healthy fishes to such an extent that they succumb to diseases that are unaffected by the treatments. Also, the use of medications such as antibiotics at lower than therapeutic levels or too often can result in drug- resistant pathogens. For these reasons treatments should only be used when indicated, and then at the appropriate concentrations and lengths of time (as stated previously).

The last point about disease treatment is that a given treatment must have a chance to work. We recommend that once a treatment is started that it be continued for three, full treatments before discontinuing it and attempting something else. In the case of treatments that require a medication to be added at least every day (this constitutes the majority of medications used as baths) this will mean a minimum of three partial water changes, and a minimum of three dosings of the medication. If after three days of treatment there is improvement (i.e. fishes stop dying) then the treatment must be extended until all signs of the disease are gone. At this point an additional one to three treatments should be preformed to insure that the disease has, indeed, been stopped. It should be obvious that some advance planning goes into a disease treatment. The most basic consideration is that one has enough medication on hand for a minimum of four treat- ments, and that a ready source has been identified should additional medication need to be acquired.

If after the initial three treatments there is no sign of improvement, or if the diseased population actually appears to be getting worse, then one needs to change treatments. Prior to actually dosing an aquarium with a new treatment the previous medication must be removed. To accomplish this one should add carbon filtration to an outside power filter after as large a water change as possible. Dyes such as malachite green and acriflavine are easily removed by this method. Antibiotics, trichlorfon and metronidazole, too, are easily removed by fresh carbon filtration. Potassium permanganate can be eliminated with a partial water change, carbon filtration and the addition of AmQuelTM. AmQuelTM will also help eliminate the last traces of malachite green and methylene blue from treated water. Copper, if not chelated can be fairly easily removed with activated carbon, but the chelated forms are difficult to remove by such means. Successive water changes are almost always the only way to completely eliminate copper from a treated system. The use of NovAquaTM to precipitate out the last traces of copper is also recommended.

Do not start any new treatments until the previous treatment has been stopped and any medications removed from the treatment tank’s water. Once a new treatment is to be started proceed just as if it were the first treatment. It is obvious that an accurate diagnosis is important.

Aquarists need to recognize the fact that many, if not most, of the popular medications sold in aquarium shops:

(1) are useless for the conditions indicated
(2) will be under-dosed if used as directed
(3) have incomplete directions (sometimes due to label space restrictions)
(4) will cause problems for established biological filtration.

For these and other reasons aquarists need to be well-read on the subject of aquarium/pond fish diseases. Aquarists should always seek out the most reliable consultants when attempting to treat a problem unknown to them. Just like with one’s own potentially fatal diseases, several opinions should be sought.

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