Can copper sulphate or malachite green oxalate kill friendly bacteria?
Oh yes most meds completely kill off the good filter bacteria. There is another solution that works just as well with out killing your filter. First you must change the water until your water perameters are ammonia and nitrite = 0 ppm. Nitrate under 10ppm. You may have to change 50-75% of the water to get your water pristine. Then in the morning add one teaspoon of non-iodized rock salt (kosher, ice cream) and crank the heat to 83 degrees. In the evening repeat one teaspoon per gallon of the salt. Repeat the same dose of salt the next morning, and evening. Keep your fish in this for 2 weeks. When you change the water replace with 1 tablespoon of salt per gallon water (equivilent to 4 teaspoons per gallon). When the two weeks are over start changing water with fresh and do not add any more salt to the water you are replacing. Bring the heat back down by 2 degrees per day and no more until you reach the ideal temperature. If you have scaleless catfishes you cannot use salt. You will have
