I bought a small hippo tang, about 1 1/2 inches on Friday October 6. I put it in a 20 gallon QT and after the first day when I made sure it was eating, I started a round of API General Cure and observation. Last night, October 10, I noticed it has Ich. I am now doing TTM on this one little fish using 5 gallon buckets. I am hoping the fish had Ich when I bought it and it was just not visible yet. Could it have been sick and it just became noticeable after 4 or 5 days? My concern is that I used some filter media that was in my sump of my DT in the HOB filter for the QT tank. Could I have infected this fish by using that filter media from my tank even though none of my fish exhibit any signs of Ich? I have a 210 that has several fish in it, one being a large Blonde Naso Tang. He has never had any white spots on him. I had to do TTM on all my fish and leave my DT fallow for 80 days ( a few extra for insurance) when I had my 55 gallon setup. I bought a fish from a LFS and did not QT it, and it had Ich. TTM took care of the Ich and I have since upgraded to the 210 about 18 months ago. In the upgrade I used the rock from my old setup, and bought new sand and some new rock. Since doing TTM and leaving the tank fallow, no fish have shown signs of Ich in my DT even after moving my fish from the 55 to the 210. I have been told that "every tank has ich in it" but I have trouble believing that. So, could I have ich in my DT and it not show on my fish?