Handling Disease Problems

There are two broad categories of disease that affect fish, infectious and non-infectious. Infectious diseases are caused by pathogenic organisms present in the environment or carried by other fish. Infectious diseases are broadly categorised as parasitic, bacterial, viral, or fungal. They are contagious, and some type of treatment will be necessary to control the disease outbreak. In contrast, environmental problems, nutritional deficiencies, or genetic anomalies cause non-infectious diseases, they are not contagious and cannot be cured by medications.

Many disease problems of rainbowfish begin as external infections. If uncontrolled, the infections may become systemic, resulting in death of the fish. Correct use of chemical treatments can effectively control many bacterial, parasitic and fungal agents before systemic infections become established.

A common mistake of many hobbyists is misdiagnosing disease problems and treating their sick fish with the wrong medication or chemical. When the chemical doesn't work, they will try another, then another. Selecting the wrong treatment because of misdiagnosis is a waste of time and money and may be more detrimental to the fish than no treatment at all. Successful aquarists learn by experience. Newcomers to the field need to learn the fundamentals of diagnostic procedures and how to identify disease.

No chemical treatment used in fishkeeping is completely harmless to fish, and should not be carried out without a thorough understanding of the potential problems that can occur. Before applying chemicals double-check the chemical you are using, the concentration to be delivered and ideally, two people should independently calculate the amount of chemical to be added.

Proper calculation of concentration is contingent upon accurate determination of volume of water to be treated. If you are uncertain as to the volume of water to be treated then take the time to measure the size of the aquarium so that volume can be accurately determined. Ideally, all chemical treatments should be carried out in a special treatment or quarantine tank.

When using any treatment for fish, a bioassay (a test to determine safe concentration) should be conducted on a few fish before large numbers of fish are exposed. Fish species can react differently to various concentrations of the chemical; therefore, fish undergoing treatment must be monitored closely for adverse reactions. If the fish negatively react to treatment, the chemical should be flushed immediately from the system, or the fish should be moved to fresh water. However, fish that do not improve as expected should be rechecked and retreated if necessary. Over treatment with chemicals can cause serious damage to fish.

A popular means of medicating fish is to place a chemical into the water with the fish. This treatment is effective for treating certain diseases, particularly parasitic infestations on the skin or gills. A predetermined amount of chemical is added to a known quantity of water for a specified time. Any time a water treatment is utilised, attention must be paid to the concentration of the chemical applied and the duration of exposure to that chemical.

Use accurate, sensitive scales to weigh chemicals when treating aquariums or ponds. If a suitable scale is not available, commonly available measuring spoons and cups can be used. Cups and spoons are not the best way to measure chemicals, but are better than using inaccurate scales. Cups and spoons that conform to an accepted standard should be used.

Most discussions of chemical applications employ descriptions of concentrations of chemicals. Concentrations of chemicals are commonly expressed in terms of milligrams per litre (mg/L) or parts per million (ppm). When making a chemical application to an aquarium, these two terms are equivalent [one litre of water weighs 1 kilogram = 1000 grams = 1,000,000 milligrams]; therefore 1 mg/1,000,000 mg (or 1 litre) = 1 ppm. One ppm refers to the addition of 1 part of chemical in 999,999 parts of water (by weight).

There are three basic water treatments: dips (less then 1 minute), short-term (about 1 hour), and prolonged treatment (indefinite). The difference between these treatments is the concentration of the chemical applied and the period the fish are in contact with the chemical. If too little chemical is added the treatment will be ineffective; if too much is added or if the fish are left in contact with the chemical too long, they may become stressed or die.

Addition of chemicals to water containing fish must be done carefully so that the entire chemical is mixed uniformly throughout the water column. If the chemical is not thoroughly mixed, areas of high concentration of chemical may be formed which can damage or kill the fish. To ensure uniform application, dry chemicals can be dissolved in water prior to application.

Remove any carbon from filters but maintain flow for maximum water movement. Aeration can be used to help distribute chemical throughout the water column. If treating in an aquarium with undergravel filtration remove the airstones or powerheads from the uplift stacks and place them in the aquarium proper to prevent the medication from passing through the gravel.

Medicated feed or injection are preferred for treating systemic (internal) bacterial infections and are based on fish weight and are expressed as weight of chemical per weight of fish per day for a specified number of days. This may be in terms of mg drug/kg fish weight/day. Improper doses may result in an ineffective treatment or mortalities. However, if the fish are not eating then a water treatment may be the only method available to administer medication.

Obtaining Medications
Medications have an expiration date beyond which they may lose their effectiveness. Light, moisture and elevated temperatures are factors that may dramatically accelerate this rate of degradation. Unfortunately, many remedies available in aquarium stores do not carry any expiration date, nor are kept under acceptable storage conditions. Warm temperatures, moist environment, or stored on shelving under bright lights are factors that will affect commercial preparations sold in the hobby. Other times it is the hobbyist who decides to use old products! These situations should be avoided.

Unless 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 or just careful observation. Wait another 24 hours until stores are open and buy a fresh package of the exact medication that you need. Here are some useful tips to consider on the subject of purchasing and keeping medications:

1. Buy medications from a shop that has a high volume of sales and stores them under acceptable conditions.
2. Stay away from dusty or moisture-stained packages.
3. Sealed containers are preferable to boxes or bottles that can be easily opened and contaminated.
4. 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.
5. Store what you bought in a cool and dry place.
6. 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.
7. Keep you aquarium medications out of the reach of other pets or children.

© Copyright Adrian R. Tappin
Created July, 2005.