DISEASES, PARASITES, AND PROBLEMS 5I 



the water is left unchanged for three weeks. Quinine 

 is toxic to plants; hence, any plants present must be 

 removed. 



Oodinium limneticum is a dinoflagellate which 

 causes a sickness commonly referred to as gold dust 

 disease. Infected fish have the appearance of being 

 covered with a golden dust. Oodinium has both at- 

 tached and free-swimming stages. The attached stage 

 is parasitic. It covers the fins and general body sur- 

 face of the fish. Infected fish become emaciated, and 

 at least younger fish suflFer heavy mortahty ( see Jacobs 

 1946 ) . Diagnosis is by the gold-colored growth ( Oodi- 

 nium possess a yellowish pigment) on the fish's body 

 and by the identification of the attached form. 



Oodinium. is especially important on young fish 

 and more dehcate species. In some cases this parasite 

 lives on adult fish vdthout causing great damage, but 

 it drastically affects young fish of the same species. 

 The author has successfully used a malachite green 

 dip at 15 p.p.m. for 2 minutes for control of the 

 encysted form of Oodinium. 



Although protozoans of the genus Trichodina may 

 heavily infest fishes, they normally do not seem to 

 cause pathological symptoms. Their occurrence is 

 easily detected by microscopic examination of the fins 

 of the fish. They can be removed by a 12-hour treat- 

 ment v^th 1 to 30,000 formalin. 



Varasitic Worms 



Most of the parasitic worms of fishes have com- 

 plicated Hfe histories involving two or three hosts. 

 Aquarium conditions are such as to prevent these 

 parasites from being a problem. Trematodes of the 



