Murray,
There does not appear to be any film or fungus on the zoos. What happens is that one or two polyps from a frag close up the first day, then more close up the second day. The polyps from the first day shrivel up by the third day are are gone by the fourth day.
But now with our established colony (about 3" x 5"), all of the polyps are closed when the morning actinics are on. This is new. Usually, they have been open almost all the time, except on maintenance day when I turkey baste the whole tank including the zoos. Anyway, most of the polyps open up by mid-day after the halides are on, but not all of them. This has been the third day I've noticed the difference in the established colony and it seems to be getting worse.
Tank parameters are Ca - 430 ppm, alk - 8 dKH, Mg - 1380 ppm, pH mid-day - 8.33. No new additions to the tank since the zoos were introduced over the past several weeks. Lighting, water flow is the same as it was in August 2006 when we amalgamated the 67g and 37g into the current 120g.
Found this page on RC that details the dipping proceedure. One post part way down says to dip every 12 days. 20g WT tank, here we come...
http://www.reefcentral.com/forums/sh...hreadid=451720