Algae, staining, dirt so on and so forth will cause them to discolor. You can take them out and bleach them, scrub them and rinse them to get the white back. If you let the sit in fresh water for about an hour then let them sit in the air for another hour they are good to go. If you are worried about chlorine you can soak them in so dechlor too. I used to do that then realized it was unnecessary.Have not chosen exact fish yet, but rare and colorful are good! Another member made suggestion above, that’s probably where I’ll start.
Background most likely that vinyl roll out stuff... not sure which setting...
I looked at the holey rock in Petco, seemed real... I ordered 4 large pieces. Comes in a few days, I did not know it doesn’t stay white.



