Fish Hatchery Management - fisheries & aquaculture

.ISH HEALTH MANAGEMENT 277aquatic environments as an algicide and also has been an effective controlfor a variety of ectoparasites, including such protozoans as Trichodina, Costia,Scyphidia (Ambiphrya), and Ich. Its major drawback is that its toxicityto fish varies with water hardness. It is highly toxic in soft water. Coppersulfate never should be used as an algicide or parasite treatment unless thewater hardness is known, or unless a test has been run to determine its toxicityto fish under the circumstances in which it is to be used. Even whereit has been used with previous success, it should be used carefully; in atleast one situation, dilution of a pond by heavy rainfall reduced waterhardness to the point that previously used concentrations of copper sulfatekilled many catfish.Copper sulfate generally is used as an indefinite pond treatment. As arule of thumb, the concentration to use varies with water hardness as follows:at 0-49 parts per million total hardness (TH), do not use unless abioassay is run first; at 50-99 parts per million TH, use no more than0.5-0.75 part per million (t.ZS Z.0Z pounds per acre-foot) ; at 100-149parts per million TH, use 0.75-1.0 part per million Q.OZ-Z.ZZ pounds peracre-foot) ; at 150-200 parts per million TH, use 1.0-2.0 parts per million(Z.ZZ-5.+ pounds per acre-foot). Above 200 parts per million TH, copperrapidly precipitates as insoluble copper carbonate and loses its effectivenessas an algicide and parasiticide. In hard-water situations, a bioassay shouldbe run to determine the effective concentration needed. It may be necessaryto add acetic acid or citric acid to hard water to keep the copper insolution. The commonly used ratio is I part CuSO4 to 3 parts citric acid.Although copper sulfate has been touted as an effective control for certainexternal bacterial infections, such as bacterial gill disease, fin rot andcolumnaris, and fungal infections, it has proven to be ineffective againstthese diseases on warmwater fish. Other chemicals are much better for controllingthese organisms.Copper sulfate should be used with great caution, if at all, in warmwaterfish ponds during the summer, particularly if an algal bloom is present.Copper sulfate is a very potent algicide, and it quickly can cause oxygendepletion by killing the bloom. Therefore, it should be used in hot weatheronly if adequate aeration devices or fresh water are available.POTASSIUM PERMANGANATE (KMNO4)Potassium permanganate (registered by the Food and Drug Administration)is 100'X, active. It is used widely in warmwater fish culture as a control forexternal protozoan parasites, monogenetic trematodes, and external fungaland bacterial infections. Because it does not deplete oxygen levels, KMnOais a safe treatment in warm temperatures and in the presence of algalblooms.