Desjardini Sailfin, Ich...

Hey guys, I just introduced a powder brown tang into my tank about 3-4 weeks ago. Current tank members: Sailfin, flame angel, cb angel, bangai cardinal, 2 clowns, 2 cleaners, 1 blood shrimp, CUC. Ive been monitoring the tangs closely to catch any ich before it got bad. The powder brown had a brief spell with ich but it never became an issue, healthy and got over it. Now my Sailfin is starting to show a few ich spots, 4-5. He has been visiting the blood shrimp more than usual however he still is eating normal, perhaps slightly less since the powder was introduced.

So I have 2 questions. First, how much nori should I be feeding these tangs? Second, When should I become worried about the condition of my tangs in regards to ich? I know they should be able to combat it if they are healthy.


Its a 150 gal 6 ft wide tank under 3 250w halides. temp average is 79 and my nitrates are a bit high 15-20ppm.