No Are you sure they are not tannin stains left there by leaves
Fiberglass. Over time concrete stains and can become rough, where fiberglass retains its smooth texture. Fiberglass will also give you more options.
Many stains can be removed with alcohol.
Yes, it does.
You can clean fecal stains from a fiberglass both by using hot water and dish washing liquid. Let the stained area soak in the soapy water for awhile before wiping it down.
I would say baking soda.
Yes
baking soda
A stained carpet can be a headache for many homeowners an individuals. Carpet stains should be removed as soon as possible - some stains can be difficult to remove if left for a long time. Baking soda can be very effective at removing most stains. A 2:1 solution of water and baking soda can remove most stains.
I have never heard of baking soda used on sharpie stains. But, I do know that denatured alcohol will break down the sharpie stains, but you will need some tide or shout spot treatment after using the denatured alcohol to pull out the stain. It worked for me!
Just increase the acidity of the water for a couple of weeks. a lot of pool stains are the result of tannin from plants and leaves and acid neutralise's it.
Any good quality rust remover can be used for rust removal on many surfices.
Cosmetics stains are very hard to remove. I had a bottle of concealer spill on my bathroom floor and I was never able to have it removed. You can try scrubbing the area with baking soda, baking soda is great for everything.