Cracked open the sand filter head and on top of the sand today I found this thick spongy stuff. I removed most of it by hand and have back washed several times about every 30 minutes today for about 3 hours. I've put algaecide in it and over shocked.
There are still some smaller pieces of this stuff on the top of the sand.
Is it time to replace the sand OR will this stuff die and get washed out as we progress?