something growing on the walls of my pool....... and bottom

[med88]

It looks like light brown dirt but if you get close, some small areas have some red/purple mixed in. Scrubbed and scrubbed - can't brush it off. I did the test with Vitamin C - no change. Took a chlorine tab and rubbed and rubbed - no change. I've super-shocked it and also added algaecide - no change. I have no idea what this is - can anyone help? Water tests at normal levels. Pool is concrete, 16x32 -- this started along the wall in the deep end and is creeping to the shallow end. It is also on the bottom where the pool takes a nose-dive to the diving well.

PS I live in Iowa, in case geographical are makes a difference.

[Backglass]

Sounds like some kind of algae bloom. Is it slimy to the touch?

Please post your test numbers so we can double-check.

[Guest]

Chlorine: 5 (I put 6 bags of shock in last night so this being a little high
today makes sense).
Br: 10
PH: 7.2
Alk: 190ppm