Can't say I've heard of that one before. Is it meant to release copper or something? The only concern I would have is that at least with a product you are dosing to a certain amount. Interesting!
I guess if it did work you would need to check if your water conditioner detoxifies heavy metals anyways.
I know the topic is snail control, but what is the long term plan for the clown loach? They can get quite large (16"), do better in groups and require a large tank (4-6'). Just curious.
I am thinking that the place that sold you the clown loach should buy it back since they provided misinformation. I clown loach in a 6 gallon? Incredible.
Otherwise contact any LFS (not the big box stores) to see if they will take them in. There should be several in your area (http://atlanta.cbslocal.com/2012/05/11/best-fish-and-aquarium-supply-stores-in-atlanta/)