How are you getting on with this?
In the last week I have experienced some uglies as well. This isn't the first time for me, but it's the first real time I have had a problem since setting up this particular tank up.
I have been intensively feeding my coral, anemones and fish lately and it appears that I have experienced a dinoflagellates outbreak.
I first noticed this on Saturday a day after a water change and it got progressively worse by Tuesday. By Wednesday I had seen enough and took immediate action first thing in the morning.
Basically I have heard conflicting information on dealing with this nuisance brown slime. Some say do water changes, some say don't, so I decided to do a water change and siphon out the crud.
Rightly or wrongly I am attributing this issue to a lack of biodiversity within my aquarium and too many nutrients in the water column.
Besides physically removing the dinoflagellates, I have slashed the feeding, despite giving in a bit today. Raised my PH and added 5ml of Microbacter7 in each day and leave the skimmer off for 4 hours whilst it settles.
Unfortunately I didn't take any photos of how crummy it looked on the sand bed and it's still only Thursday, so will see how it goes over the next couple of days.