Pump strainer lid and Iron Stain?

[Zenghaidong]

The lid is so tight that there is simply no way to take it off by hand.
I did some research, and bought a opening tool. But I realized that there is no enough space before/after the strainer to exercise the opening tool (see pictures below).

There are some stain on the top of the pool tile. I think it is the iron stain. Is there are any way to get rid of it?

Anybody can give me some advises?
Thanks!

 

[ajw22]

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Create a paste of Vitamin C and put it on the suspected iron stains and see if it lightens. Those stains look thick enough that it may take multiple treatments.

You know where the iron cane from? You have your pool water tested for iron?

I think you have to create an opener for your pump lid out of wood that is a length that works. Then you may need to tap it gently, or not so gently, to open it.