From experience Chemiclean is an excellent product that does exactly what it is supposed to. I have used it several times over the years.
In a 400 gallon system several times recently.
I have dosed it twice only once and did not do a water change between.
If you break up the worst mats the morning of the second day and agitate areas that are still matted so the Chemiclean can get under them you wont have to ever dose twice.
The one time I did dose it twice I suspect I underestimated the working volume of my system a bit. If you aren't sure
add 10% to the dose next time.
When you are ready to remove it the best way is to let the skimmer explode and drain it into a bucket while your ATO pump is in a bucket of new saltwater. Let the ATO keep the tank full until the skimmer comes back to normal. That way you are doing a water change but with the Chemiclean concentrated by the skimmer.
I can be over with in a half a day.
I have read most of the cyano threads on here and I am pretty sure no one knows how to prevent cyano.
Too much of this or too little of that. I can cause it almost instantly in my tank by decreasing my NoPox dose. Once it is there nothing seems to reduce it again.
More interesting is the fact that I have 3 tanks on my sump. I will get cyano in one or the other at times. I have never had it in all of them at once. When I get tired of looking at it I hit it with Chemiclean and it is gone in a few days.