Thanks for all the help here, and I must apologize for turning a thread about a thermometer into one about ich. Today was the 6th day of treatment and I have seen an improvement, meaning fewer spots. I was thinking that each fish that was infected was probably infected at a different time, or even a different day, and that would account for the difference in time for the spots to go away on each fish, considering the life cycle of the parasite. I was concerned about overusing the medication , Ick Guard, so I called the 800 number for Jungle products. They recommend treating for 5 days, then skip a day, then treat for another 5 days. I have also read that I should continue treatment for several days after all spots are gone to kill the free floating form. This has been very challenging. I thought by now it would be gone, but as said earlier by Duane, it can take several weeks to eradicate. My worry is, is it safe to medicate for several weeks? I have been doing water changes between treatments as directed, and all carbon has been removed from filters.