If it is Ich you still have it in the tank. You may want to check this article
for more information and pictures of a heavily infested fish. Ich looks like a grain of white rice on a fish, just smaller. The author of the article also claims that FW
dips are ineffective (based on other research).
"Stress and poor water conditions do not cause marine "Ich", although they will lower a fish's resistance to infection and impair their immune system. If C. irritans is not present in a tank, it doesn't matter what how stressed a fish may be, it cannot get infected. In a tank where parasites are present, stressed fish are more likely to show signs of "Ich" before more healthy fish, but the healthy fish are just as likely to become infected as the numbers of parasites increase. Those fish species that are less susceptible to "Ich" or those individuals that have an acquired immunity, may show no signs and may not get infected. "
The only way to get rid of Ich is to remove all fish from the display tank and treat them. I prefer hyposalinity unless the outbreak is severe. The display tanks should remain free of fish for 6 weeks or more, which is the amount of time you want to treat (4 weeks) and watch (2 weeks) your fish in QT
before putting them back in the tank.