lot of good advice i got from that thread, one method i never ended up trying was chin lees' hot water in bottle with straw method, never hurts to try. michika did you ever end up removing any sand at that time?

I never tried the hot water method, I was to afraid for my coral and clam collection.

We pinpointed the issue as my rocks, and once we did that I never removed the sand. However when I moved from my original GHA infested tan to my current system, I did not re-use the sand. In the end I don't think the sand played any role either with with my particular outbreak, although this probably doesn't hold true for everyone.