No skid patches that come on the bottom of the tub.

Use Easy Off No Fume Oven Cleaner in the BLUE can. Works on enamel, porcelain, and fiberglass.

We use Scrubbing Bubbles on the tub. Spray it on and walk away. Come back in a half hour and wipe it all up.

I know, texture is always hard to clean. I used Soft Scrub and a scrub brush on mine when I had it. Here's a tutorial on a recommended method:

https://www.hunker.com/12000948/how-to-clean-the-textured-bottom-of-your-bathtub

Can you remove & replace them?

I have in one tub and hate. The only thing that has consistently worked for me and isn’t a tremendous amount of work is wet and forget shower.

Make a paste of blue dish soap and baking soda. Rub onto the patches and let sit for a few minutes. Then add vinegar (I said it) and when the bubbling stops, scrub with brush and you should be good to go.

Can you put a tub mat over it in the future to try to prevent stains or at least hide them?

I would try Young Living's Thieves cleaner

Did the soap, baking soda, vinegar combo work? If not, maybe try a citric acid descaler like this one: https://amzn.to/3gb2wiA

These tubs require scrubbing each time (or at least every other time) they are used. You could try Wet n' Forget for showers. Once clean, use Bon Ami with a microfiber cloth, after use. Note that use of body washes or shower gels can cause a film build up on tub surfaces, making them slick and more difficult to clean.

I always used cleanser like Comet and a toothbrush. They are textured and the soap and dirt build up in the crevices. Try Awesome purchased in most dollar stores. Spray bottle of 16 oz. for $1 that cleans things that other cleaners will not touch. Spray one let it sit for about 30 seconds, go over lightly with tooth brush.

Blue can has less fumes. Both work equally well but fumes are quite harmful in the yellow can.

Did you try TSP substitute in a spray bottle mixed with water? With a scrubber, that might do the trick.

Hello there,

Well I would suggest you have cleaned them as much as possible, now is the time to paint them! Best wishes.

There is a product called Spray Nine. It is available at Home Depot, Walmart, or on Amazon. This is my go to for rental properties when nothing else works. It is a miracle. Spray it on and let it work for a few minutes before scrubbing with a brush. I can't guarantee it will work, but it has cleaned everything I have ever tried it on.

Just ordered it! thank you.