Blue algea?

Lately I have noticed there is some blue soapy substance that's attached to the grout lines between tiles. I can scrape most of it off by my finger but part of it seems to be embedded to the grout.

Is this some kind of algea? My pool water seems to be crystal clear and I always shock my pool once a week.

I am using a salt chlorinator, pool pump runs about 11 hours a day, pH bounced between 7.2 and 7.8 (I added acid every three to four days). I do have a low chlorine problem though, so that's why I shock the pool once a week.

Bumping this post to the top........

I've never seen blue algae (but that doesn't mean it doesn't exist!). I'll have to do some researching on that.

There is a form of water mold that sometimes grows that is a milky white, that I supposed could look bluish if you have blue tiles, but if you're shocking the pool once a week I'd be really, really surprised to find mold in your pool. Have you by any chance ever used Bacquacil, Softswim, or any of the other non-chlorine "sanitizers"?

Janet