Awesome looking SPS nissan. How long have the zoas been in your tank? Are they opening up more and more every day or do they seem to be stuck like 1/4 open and thats it?
I always iodine dip my corals, I NEVER FW dip them. IMO its counter productive to much stress. My goal when I dip is to not only rid the coral of any pest should they exist, but to also give it a nice dose of iodine like a boost. It helps IMO and mine have all opened much faster after a nice dip. You can use Kents iodine, I use Lugols Coral Dip. Its basically just a concentrated iodine. When I used kents I would fill a container up with enough water from my tank to submerge the coral in. Then I would add the iodine to the water until the mixture turned tea color. As for Lugols I followed the directions on the back. 40 drops per gal for a dip, I just reduce the drops for the amount of measured water i use. I dip the coral for 10 minutes, rinse it with clean SW and put it right into my tank. Within an hour the zoas are usually starting to open. HTH... I hope yours open soon they look like like a paly of some type, and big too.