hey everyone bought the green mean killing machine uv sterilzer for my tank on the 1st of this month, its been doing its job up until now. i bought this because my tank was invested with ich! (all my fish died part from blue wasse) i bought 2 tangs yesturday both looking fine at the LFS the following day the yellow tang had white spots all over it!!! how they got there in the space of 24hrs?, surly its not from my tank already? the blue tang is fine at mo? stress? i thort the uv sterilzer would of killed all the ich in 7 days, any suggestions? HELP!!!