FISH HEALTH MANAGEMENT 269 



organisms present. Medications hold disease organisms in check by retard- 

 ing their growth or even killing the pathogen but, in the end, it is the 

 fishes' own protective mechanisms that must overcome the disease if the 

 treatment is to be successful. To cure a disease, not just treat it, the body 

 must be helped to do the job itself. To be successful, every fish culturist, 

 farmer, or hobbyist must keep this basic principle in mind every time a 



treatment is considered. 

 Before treatment is begun, the following questions should be asked; 



whether or not to treat depends on the answers. 



1. What is the prognosis, i.e., is the disease treatable and what is the pos- 

 sibility of a successful treatment? 



2. Is it feasible to treat the fish where they are, considering the cost, 

 handling, prognosis, etc.? 



3. Is it worthwhile to treat or will the cost of treating exceed the value 

 of the fish? 



4. Are the fish in good enough condition to withstand the treatment? 



5. Does the loss rate and severity of the disease present warrant treat- 

 ment? 



Before any treatment is started, four factors must be considered. The cul- 

 turist must know and understand (l) the water source, (2) the fish, (3) the 

 chemical, and (4) the disease. Failure to take all these factors into con- 

 sideration can result in a complete kill of all of the treated fish, or a failure 

 to control the disease with a resultant loss of many fish and wasted funds. 



(1) Water source. The volume of water of the holding or rearing unit to be 

 treated must be calculated accurately before any treatment is applied. An 

 overestimation of the water volume means too much chemical will be used, 

 which probably will kill all the fish. An underestimation of the volume 

 means not enough chemical will be used, thus the disease-causing organism 

 may not be controlled. Water-quality factors, such as total hardness, pH, 

 and temperature, will increase the activity of some chemicals and decrease 

 that of others. In ponds, the amount and type of aquatic plants present 

 also must be taken into consideration before any chemical is applied. 



(2) Fish. Fish of different kinds and ages react differently to the same 

 drug or chemical. Certain species are much more sensitive to a particular 

 chemical than others. The age of fish also will affect the way they react to 

 a specific treatment. 



If a particular chemical or drug has never been used to treat fish at the 

 hatchery, it is always a good idea to test it first on a small number of fish 

 before an entire pond or holding unit is treated. This can be done in tanks 

 or in small containers such as large plastic wastebaskets. 



(3) Chemical. The toxicity of the chemical should be known for the par- 

 ticular species to be treated. The effect of water chemistry on the toxicity 

 of the chemical also should be known. Some chemicals break down rapidly 



