I lost about 16 fish when I first started, my fish had white spot, and I tried the normal WS treatment using one drop per gallon as suggested on the label, this did not shift it, then I started using something called White Spot Plus and that did seem to be affective, but, rather too late for many fish after about 2 weeks of treatment. Then I noticed a problem on one of the fins of one of the fish recognised it as fin rot, so I used fin rot and suddenly many of them died. I later heard that certain fin rot solutions can have an adverse affect on some fish and the water could become toxic. I managed to save the rest of the fish by moving them into another tank.