Don't let hard water deposits and other build-up accumulate in your bathroom toilet tank due to constant exposure to water. Use Instant Power Professional Toilet Tank Cleaner. Just like the toilet bowl needs to be cleaned, so does the tank. Build-up can cause the toilet tank to look dirty and damage toilet components. Instant Power's flush cleaner easily removes the build-up of potentially damaging deposits, such as calcium and rust, that can affect the moving parts of a toilet tank. The strong citric acid formula removes hard water deposits and other stains in your toilet tank.