I don’t know, I guess because I assumed the other fish that were in QT with her would have spots by now as well. We just added 4 other new fish 4 weeks prior to that and none of those got spots either. We have 3 QT’s so we’re pretty regularly adding new fish. We had had a case of velvet and ran fallow for 3 months so all our fish are relatively new fish and not really old timer residents except for one 6” yellow tang who has never had ich and a watchman goby) Plus I know having a larger tank and a U.V. helps with parasites as well. I know Hippos are notorious for ick but hoping it’s just stress and she can fight it off. I feed 2-3 times a day (because we have wrasses) a mixture of frozen foods (rods, krill, mysis, brine, plankton, sometimes blood worms and a special green type of brine) soaked with vitamins and garlic, nori, algae, algae cubes as a treat and the good protein pellets, the name escapes me now but it’s what everyone recommends. I also toss in algae flakes and hatchery diet. Our water is extremely stable and our water is very clean from the U.V./Carbon so clean we are overrun with sponges. I’m praying she doesn’t have more spots tomorrow but if she does I will pull her and treat her and any other fish that show symptoms.