I've been running my 120g reef for over 2 years I can't keep a tang for a day without ich creeping in. I've lost a yellow,a powder and blue one by one same crap. All my other fish occasionally might show signs but get over it. I hadn't seen a sign in a few months and figured it was done with. I bought a beautiful healthy purple tang. Quarantined him for a week and when I put him in dt. Boom! Ich spots in 24 hours I can't catch him to treat with copper so he's a goner in the next few days. My water parameters are perfect, no stress to these tangs from any fish. Temp fluctuates about 3-4 degrees. What can I do? Help my next tang, please.