Many moons ago when I had the toilet tank assembly rebuilt, I put toilet magnets in the tanks. Then I forgot about them. It is not like I look in the tank that often.
The other night when I heard the toilet running, I knew that the flapper wasn’t closing properly. When I opened the tank lid I expected to see “rusty” water as we do have very hard water where I live. When I reached down into the tank to reset the flapper, I found rocks, not just rusty water. When I swept up the rocks, wondering where they came from, I rediscovered the toilet magnet. The magnet was covered with tiny rocks and rust. Seems they were doing what the manufacturer claimed they would do, gathering the minerals in the tank to keep the bowl from looking rusty and stained.
After looking at the spent looking condition of the over a year old magnets, I ordered new ones. The photo above shows the difference in the old and new magnets. The one on the lower right was from the tank that was used the most this past year and the one on the lower left is a new one. The top one is old and from a rarely used tank. You can see the difference a magnet can make. The rust is on the magnet, not on the tank.
Another “how about that?”