FISH HEALTH MANAGEMENT 319 



results on catfish when it can be used safely. Potassium permanganate 

 sometimes is used at 2 parts per million and repeated on alternate days for 

 two to four applications. Success is not always good. Formalin at 15-25 

 parts per million can be used on alternate days for two to four applications. 

 The higher concentration gives the best results. This is a very effective 

 treatment but is expensive for treating large volumes of water. 



Prolonged bath or flush treatments can also be used to treat Ich on fish 

 being held in tanks, raceways, or troughs. Formalin is effective at 167-250 

 parts per million, depending on water temperature and species and size of 

 fish, for up to 1 hour daily or on alternate days. The number of treatments 

 required depends on the water temperature. 



CHILODONELLA 



Species of Chilodonella are small, oval, colorless protozoans, 50-70 microme- 

 ters long, which may be found in vast numbers on the skin, fins, and gills 

 of goldfish, other warmwater species, and salmonids. Under high magnifi- 

 cation, faint bands of cilia can be seen over much of the organism (Figure 

 91). Their optimal water temperature is 40 to 50°F, making it particularly 

 troublesome on warmwater species during cold weather. Heavily infected 

 fish are listless, do not feed actively, and may flash. Chilodonella is con- 

 trolled easily with any of the following treatments for external protozoan 

 parasites: 



(1) Formalin at 125-250 parts per million for 1 hour in tanks or racesays. 



(2) Formalin at 15-25 parts per million as an indefinite treatment in 

 ponds. 



(3) Copper sulfate at whatever concentration can be used safely in the 

 existing water chemistry as an indefinite treatment in ponds. 



(4) Potassium permanganate at 2 parts per million as an indefinite treat- 

 ment in ponds. The treatment may have to be repeated if heavy organic 

 loads are present. 



EPISTYLIS 



Species of Epistylis grow in clumps at the ends of bifurcate, noncontractile 

 stalks (Figures 92 and 93). Under the microscope they appear much like a 

 cluster of bluebells growing on a stalk that is attached to the fish by a disc. 

 They commonly are found on the skin but also may occur on gills and incu- 

 bating eggs. Flashing actions by the fish during the late morning and late 

 evening hours are among the first signs of infestations. Some species of Epi- 

 stylis evidently cause little tissue damage but other strains cause extensive 

 cutaneous lesions. Epistylis should be removed when it causes severe flash- 

 ing or skin lesions that may serve as openings for fungal or bacterial infec- 

 tions. Epistylis can be extremely difficult to control on warmwater 



