I have one and find it priceless. It just makes the water beautiful, aside from cleaning up clouding are floating algae problems.
I admit that I never inhale deeply over my open bag of diatomaceous earth. Interesting, I was running low on powder last week so I went into a huge store called Aquarium Adventure in Hofman Estates and asked if they carried it. The kid working the floor gazed knowingly at me and said "You can't get it any more because it causes cancer." I replied "Golly, that must have put that company right out of business!" and he nodded solemnly.
So I left, went on line, and ordered 5 pounds directly from Vortex.
My DHL tracking number shows that it arrived today and should be waiting for me at home. Hopefully I've thwarted a less than forthright retailer.