I have 2 blue tangs and I've noticed they have ick, yet again, for the 4th time. I have a strip of green algae with garlic in it, and am feeding them brine shrimp 2 times a day. Nitrites, ammonia, Ph, are all within normal limits. Nitrates are a little high at 40 (per mardel 5 in 1 test kit). I have a UV sterilizer running on the tank, and I am adding vitamin c, probuffer and purple up to the tank 2 times a week. What else can I do to save my fish besides qt again?