After opening to a major swamp last spring, I looked for advice on preventing the same from happening this year. A local service guy told me to add 6 gallons of clorox in the spring, three at each end. So as soon as the ice was gone in the middle of March I peeled back the cover and added two 182oz bottles at each end, stirring with a 2 by 4 to distribute it as much as possible. I also went out on my own and put 4 trichlor pucks in a floater and tossed it in (anchored with a string and kid's toy to keep it away from the vinyl liner) but I really had no idea how much chlorine that would add or how long it would take to dissolve, just wanted to make sure algae wouldn't have a chance.
A month later in mid-April the water was still just below 50 degrees, the pucks were basically gone from the floater, and the chlorine level near the surface was 12ppm (CYA near zero). Yesterday the chlorine level was down to 6ppm. The mesh looploc-type cover does let some light in.
Having leared alot here I'm now wondering how dumb this was... 6 gallons of 6% bleach would add 15ppm chlorine, and the four 8oz pucks added another 8? which isn't crazy but it's unknown what the level was at the bottom of the deep end if the bleach pooled down there. Did I shorten the life of the liner for nothing? Is it smarter to just open early if you see green? Or use polyquat first thing in the spring?
On the plus side I'm getting ready to open and have to say the water is super clear!