I have a recently installed sand filter for my 28k gal IG pool. For the previous 10yrs I had a cartridge filter, that worked fine up until last year. The algea was so bad then, and the earlier part of this year, that I was spending too much time dismantling the filter and cleaning the cartridges for my liking, hence the switch to sand. (I also switched to SW as well.) The sand filter does not do as good a job as the cartridge filter did. I heard that there is some kind of a cellulose additive I can put it the skimmer that would improve the filtering capability. Has anyone else heard of this? Is it recommended? What is it called and who sells it online?