stains on a gunnite pool surface.

[Pool_Fool]

I am helping a buddy of mine open his 8000 gallon pool. We are noticing some extensive staining on the bottom and walls of the pool. Please see the attached picture. The pool is suppose to have the blue look to it and not the reddish dirty look.
Any thoughts or suggestions on removing.

Salt 2900
Ph 7.2
Alk - 60
Cal - not tested yet
Cya - 40
Fc - 20(just shocked again)

Tia,
PF

 

[jblizzle]

You need to identify whether the stain is organic or metal and then we can offer the path forward.

Organic: A trichlor puck will lighten the stain in a few minutes
Metallic: Crushed up Vitamin C will lighten the stain in a few minutes

 

[Pool_Fool]

Thanks will do.

 

[Pool_Fool]

Have not run the stain test yet....but the pool is ripping through the free chlorine.
Went through 20ppm in two days.

Pool clarity is at 90% but I wonder if there is a chance the "stain" is active algae,
Or if there are little pockets of algae hiding

...thoughts

 

[jblizzle]

Are you brushing while you are in the shock process?

 

[Pool_Fool]

No.
Should I use any type or should i use an algae brush.
We have brushed it a couple of times and doesn't move but we are using a plastic one.
We should probably upgrade, yes??

 

[jblizzle]

If the plaster is over a year old, you can use a stainless brush or a combo one.

 

[Pool_Fool]

The pool has undergone the shocking and brushing process since last post.
It is still burning through the Free Chlorine, I last shocked and brushed it this am.

I did perform the stain test with the 3" puck, it sat on the pool bottom for 5+ minutes there was no reaction.
I have not yet tried the Vitamin C test, but wouldn't the lack of a result from the first test have us lean towards it being a Metal Stain
at this point?

Thanks again for all the help.
PF