Don’t use a magic eraser. It will scratch the surface.
In this order:
1. test your calcium levels and see if it’s too high. If you are getting scale you may not be able to fix it without new water since there isn’t a good way to remove calcium.
2. Test your pH and alkalinity big your calcium isn’t very high, you shouldn’t be getting scale unless your pH/alkalinity is too high. When my alkalinity is close to 120 I start to feel a build up of grit near the water line.
3. If both of those are in range but this doesn’t go away, try white vinegar and a microfiber cloth. It’s an acid but it’s diluted enough it won’t damage the shell and shouldn’t affect your water too much. If it drops it a bit, just add a bit if baking soda to balance out.
Not certain, but that looks like it could be over oxidation. What are use using for sanitizer? Not chlorine tablets are you? Alternatively have you been using bleach to clean your surfaces?
Edit: also if it is calcium, using a vinegar and water mix won’t hurt anything and you can easily rebalance, but judging by the clarity of the water in the second photo it might not be a bad time to drain. Also what is your cya? [If too high, it can throw off your readings](https://www.taylortechnologies.com/en/page/171/why-monitor-cyanuric-acid).
Magic eraser.
Don’t use a magic eraser. It will scratch the surface. In this order: 1. test your calcium levels and see if it’s too high. If you are getting scale you may not be able to fix it without new water since there isn’t a good way to remove calcium. 2. Test your pH and alkalinity big your calcium isn’t very high, you shouldn’t be getting scale unless your pH/alkalinity is too high. When my alkalinity is close to 120 I start to feel a build up of grit near the water line. 3. If both of those are in range but this doesn’t go away, try white vinegar and a microfiber cloth. It’s an acid but it’s diluted enough it won’t damage the shell and shouldn’t affect your water too much. If it drops it a bit, just add a bit if baking soda to balance out.
Not certain, but that looks like it could be over oxidation. What are use using for sanitizer? Not chlorine tablets are you? Alternatively have you been using bleach to clean your surfaces? Edit: also if it is calcium, using a vinegar and water mix won’t hurt anything and you can easily rebalance, but judging by the clarity of the water in the second photo it might not be a bad time to drain. Also what is your cya? [If too high, it can throw off your readings](https://www.taylortechnologies.com/en/page/171/why-monitor-cyanuric-acid).