Rust spots bottom of pool liner

[Mattyssox]

Hello,

I dove down today into the pool with goggles and saw some rust spots. I thought maybe black algea but they didnt wipe away.

questions,
what is most likely the cause? and how do i know if its a big deal or a one time deal(or can this rust sort of expand..sorry if thats a bad question)

is there a safe way to clean them (pool is obv full of water etc).

As always thanks for your help

 

[PAGirl]

Could anything have layed there over the winter? Were they there when you opened?

 

[Mattyssox]

I am thinking it was something in there over the winter. I've spent the last 30 minutes replaying the entire opening and shocking process. I think a brush may have been in there. But can it expand or is it a one off.

 

[Richard320]

Once the metal is removed, the stain should stop spreading. The tiniest but of iron or steel can leave quite a large stain. Some Vitamin C tablets piled on should lift it. Check out this picture: