I seem to be getting results with my theory. I had an algae or cyano growing. I didn’t suspect Dinos because my nitrates are consistently at 20 and phosphates are between .09 and .17.
I decided however to steal Some part from the Dino playbook.
My theory is my good bacteria may be weak or being out competed by less desirable bacteria.
It a bit anecdotal but I used chemiclean the first round (worked great and my coral loved it). I added a small bit of good bacteria. After two weeks I got another round of something and my zoas closed up tight.
My theory is that the chemiclean killed good bacteria as well as bad. Now there was room and another surviving bacteria took over.
As an experiment I did the following
I shut off my lights for a week (not a blackout)
I then added bacteria to the tank. While the lights were off but a few days into it. I then added seed bacteria daily (I had it in hand so why not). I also did not do a water change. So far the result is my sandbox is white and clean. My corals are starting to open up. My snails are now back to cleaning the sand bed as well (notice my plugs are pushed out).
I plan to continue the regimen of adding bacteria weekly for as long as the directions state. I will be interested to see if it is working.
Super clean sand bed
Started to open
Still need time
Be warned it stink like a neglected skimmer