I thought it was like fired clay, but didn’t know it actually was. The stuff scratched the heck out of my bathtub so I know it’s not too soft or chalky.
Anyway, it’s a chore and I think Id rather wash…umm…anything else. However, I found the trick was to wash a little bit at a time (like 1/6 of a bag) in a 5 gal bucket. Rex had mentioned a paint strainer, but I couldn’t get my hands on one and had to adapt. It takes a while, but it will run pretty clear.
In any case, I know a sure-fired way to test if it is the Fluorite or not clouding your tank. Stick a magnet cleaner on the same side of the tank as the filter intake (or close to it). If its Flourite floating in the water, you will soon have a red/brown Fluorite film all over the magnet because the stuff is magnetic.