Summerville SC says "HI"

Welcome back!

Sand algae... :scratch: Do you have algae in your filter or something?
 
it's algae that builds a "shell" and attaches to all surfaces under the water line. It's crazy weird. the only way to diagnose is to get scrapings of the "shell" in a glass jar, add distilled vinegar and wait until the foaming stops. If it's sand algae, you'll see a coating of very healthy green algae on the bottom of the jar.
I replied to my own post about "Calcium scaling problem? bad!! :( in the algae forum list. It has pictures when my problem started 4 years ago.

http://www.troublefreepool.com/threads/24764-calcium-scaling-in-vinyl-pool-bad-(