There are a number of other complaints, obscure and rare, to which the fish is liable, but their diagnosis is so difficult and their cure so problematical that I will confine my remarks to the common complaints, especially those that may yield to treatment.
White Fungus (Saprolegnia) is often brought on by a fish bruising itself. The spores are nearly always present in pond water and only await a favourable opportunity to manifest themselves. Even without exterior injury, an unhealthy fish is open to infection.
The disease shows itself as small white tufts, like pieces of cotton wool, adhering to the fins and body. The gills are attacked in the final stages and this is fatal. The fish should be removed from the pond and placed in a salt water bath. As this is the best all-round treatment for sick fish, I will describe it in detail.
Into a shallow dish of fresh water put salt in the proportion of two heaped teaspoonfuls to the gallon of water ; keep the fish in this solution for three days, changing the water daily and increasing the salt content by one teaspoonful each day. If the fish turns giddy the salt should be decreased. After three days remove the fish to a damp cloth and, with a soft brush loaded with weak iodine, brush off the fungus spots. The fish may be transferred to the pond, but if it shows signs of sickness still, the treatment can be repeated a week later. In the meantime it is advisable to disinfect the pond with permanganate of potash, the other fishes, of course, and the snails being first removed. The permanganate will not injure the plants.
If the other fish are placed in a bath to which has been added a small quantity of salt any spores lurking on their skin will be killed.