In the June 1991 issue of Nichirin magazine is a report by Takayuki Izeki on using a very concentrated saline solution as an effective treatment for "hole" disease. The infected koi can either be immersed (very short bath) in a very concentrated (saturated) salt solution (10 parts of salt to 90 parts of water) or the infected areas can be painted with the saturated saline solution. In addition it is recommended that an injection of Gentamycin be administered. The author feels that the saturated salt solution is more effective than potassium permanganate, malachite green, tetracycline, etc. With the immersion method, immersion time depends on the size of the koi and the temperature of the water. Both are critical. If the pond temperature is 25°C (77°F), immersion time for a koi 30 to 55 cm (12 to 22 in.) is 5 seconds; 6 - 7 seconds for a koi measuring 55 to 70 cm (22 to 28 in.); 4 seconds for a koi under 30 cm (12 in.). If the pond temperature is below 20°C (68°F;) you may add 1 second. An alternative is to anaesthetize the infected koi and liberally "paint" the infected area with the saturated salt solution. Then let the treated infected area be exposed to the air for 2 - 3 minutes before returning the koi to the water. You can keep the rest of the koi covered with a soft towel soaked with pond water. If the disease is bad, repeat the treatment in 5 days. In addition it is necessary to improve the pond water quality. i.e.: partial water change and clean excess organic debris from filter and pond bottom. Recent Z.N.A. research indicates that a concentration of nitrites above 0.5 ppm contributes to the disease. This is because their research indicates Flexibacter Columnaris is the primary infection, and takes nourishment from nitrous acid (nitrites) to reproduce. The protozoan parasite Epistylis is the secondary infection with Aeromonas as the third or final stage. Although most recent literature mentions Epistylis protozoa as a cause of ulcer diseases in fish, most hobbyists in the USA only treat for bacteria when treating "hole" disease.