Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
Never used Clarity so can't speak for it.
As for Purigen, I've used it for many years, 24/7, mainly in planted discus tanks, and I can't imagine how you could improve on it for producing unbelievable water clarity, and truly superb water quality based on all the undesirable elements it regularly adsorbs.
I swear by it and wouldn't use anything else (after trying a couple of other products said to produce the same results).
And Purigen, based on my experience, has never removed ferts or other essential natural needs of plants, nor has it had any effect on altering appropriate GH and KH levels in a tank.
Never tried this, but I believe Purigen can be somewhat effective simply being placed in a bag somewhere in the tank, but not nearly as effective as being placed within a filter with a good water flow moving through it for best adsorption, which is how you're supposed to use it.
You can buy Purigen in bags, or by loose beads by the jar that you can bag yourself in an appropriately-sized fine mesh bag.
As I've said, I've not used Clarity, but I don't see how anything can improve on what Purigen can do.
The name "Clarity" by definition tells me what it's main purpose is.