FISH DISEASES 93 



chrome may be applied, full strength, to the body and fins, using a little 

 absorbent cotton, held in tweezers. Some aquarists successfully use salt 

 instead of Mercurochrome, 2 teaspoonsful to the gallon, in conjunction 

 with the heat of 85 degrees. 



The disease principally affects tropicals. 



Tropical fishes are the principal victims, and attacks are usually 

 caused by the water becoming chilled, or by the use of unseasoned water, 

 or by sudden temperature changes, either up or down, but mainly down. 



Goldfishes yield to the same treatment, or may be given the per- 

 manganate of potash treatment as described under "Fin Congestion" a 

 few pages back. Then again they have simply been wiped off goldfishes 

 with a piece of cheesecloth dipped in kerosene, placing the fish in new 

 water and a new receptacle after treatment. A repetition on the second 

 day is usually necessary. 



Thread Parasite. Although the Lernean parasites of many species 

 have long been known to science, and are indeed quite common both 

 to fresh and salt water fishes, it was not until 1931 that this pest made 

 itself apparent to fish farmers. The first manifestation is a pimple, 

 commonly near the tail. From this develops a tough thread-like growth 

 about half an inch long, usually with a slight branching at the end. It 

 is anchored deeply in the flesh of the fish with a small spreading foot, 

 and when removed by a steady pull, leaves a sore which heals itself, 

 but which had best be touched with a bit of mercurochrome. If not 

 removed the parasite will presently die and drop off, but the numbers 

 very greatly increase if nothing is done about it, so that they attach 

 themselves to all parts of the body, even into the mouth, when the 

 results may be fatal. The outer end of the thread contains an egg sac. 

 The young become free-swimming and burrow into the flesh of the fish, 

 which starts the described pimple. Treatment consists in picking off 

 all the threads, removing the fish to another receptacle and treating their 

 tank with a tablespoonful ,of chlorinated lime to each gallon of water. 

 This will kill practically all life in an hour. Flush tank and refill. If 

 convenient, the fish should not be returned to their tank for two days, 

 to see whether embryo parasites already in the fish develop. Where the 

 foregoing treatment is impracticable, it is advisable to try the perman- 

 genate method as recommended for Fish Lice. 



Diseases of Tropical Fishes. Tropicals usually cannot so well stand 

 the different chemicals and treatments recommended for goldfish. The 

 principal cause for their lack of condition is too low a temperature. If 

 placed in a uniform warmer temperature, with one ounce of sea salt to 

 each gallon of water, and fed up on daphnia, small chopped earthworms, 

 or white worms, they will usually improve rapidly. 



