Water parameter are in check, i do monthly 30 gallon water changes. The blue tang has been doing great for months, then i added a new chevron tang(also has ich) about three weeks ago and the blue tang has went downhill the last 3 days. They both eat like pigs, lets hope they are healthy enough to pull through. The chevron does not look bad, but the blue looks real bad on one side. All other fish show no visual signs of ich. I think my tomato clown is harrassing him causing it to stress. I have not seen it scratch, but that could be the problem.