I have 4 small, about 2 inches each with their tails, fancy goldfish in a 30 gallon tank that contracted ich due to not quarantining 3 newcomers. Started them on quick cure (malachite green and formulin) 6 days ago, and am still continuing treatment. Doing a 25% vacuum water change every fourth day as package recommends. Dosing daily every 24 hours as package recommends. Water temperature was raised to 78 degrees, My heater would push no higher than 78. There has not been carbon running in the filter. Aquarium lights were kept off. I noticed on day 1 that the water did not seems to stay colored (dyed) for more than an hour, so that evening I removed all the live plants and all the gravel (natural). I assumed they were absorbing the meds. The ich started with just a few spots. On day 3 the fish were spot free. On day 4 there were a few spots again. I continued the meds. Day 5 I decided to cover the tank with towels to keep it very dark. This has made the dye in the water more pronounced and has raised the water temperature to 82 degrees. The fish have more spots today on day 6 than ever before. Reading various sites on the internet, this is supposed to be one of the most effective ich treatments on the market. Can anybody tell me what is happening? A resistant ich stain maybe? Should I change treatments? If so, does anyone know how long it takes to filter malachite green and formulin out of my tank if I replace the carbon in the filter? It has been 6 days and things are getting worse instead of stable or better. I had originally thought of going with a salt treatment, but I have always run small quantities of salt in the tank and was afraid to overdose. I assume most of the salt is gone now after all the partial water changes. Fish are still eating and are active. Ammonia & nitrate levels are 0. Please help. I would really like to save them.