I think anyway. It looks browinsh in the water but what is on the cartridge filter is yellow slime. Question is how long should it take? I used a copper-based treatment this morning. I changed out the filter, brushed then mixed 2oz (my water volume is only a shade over an ounce needed) in 2.5 gal of water and poured about 3/4 of that mixture around the edge of the pool. The brushing stirred up what was on the bottom of the pool but it looks like it is either settling back down or reblooming. How fast does this stuff grow?