What is it?

[waste]

Not so sure about 'good', just concious . In the course of my work I see the same stuff in almost every pool with a 'stamped' deck, hope this puts your mind to rest on the 'stuff'.

[CanuckPool]

I thought I had another exxon valdez on my hands

[smallpooldad]

Lived in Central Los Angeles for three years.

The pollution settled onto the pool daily. This is potentially what it might be - soot.

We used to scrub it out.

Aloha