3 things; 1; Citric acid is a natural cleaner that can help break down mineral deposits, stains, and grime in the toilet bowl. It’s effective against hard water stains and limescale buildup, making it useful for maintaining cleanliness. To use citric acid in the toilet, you can sprinkle some into the bowl, let it sit for a while, and then scrub with a toilet brush before flushing. However, it’s essential to use it in moderation and not mix it with other chemicals to avoid any adverse reactions..