Interesting....very interesting. Has anyone used any brands other than special kitty? If I wanted to try this in an already running tank, would I have to completely drain it out and start over to put it in, or would I be able to just dump it in and then spread a layer of gravel over it? The tank I am thinking of is currently a mix of pea gravel, playground sand, and locally collected pieces of 'pretty' rocks (jasper, agate, and a bit of amethyst) Also, someone mentioned that it can cut up shrimp. What about fish that spend a lot of time on or in the substrate like cories and loaches? I have a small kuhli loach that spends most of his time burrowing, and I don't want to hurt him.
I also had another interesting thought today while starting some seeds for my vegetable garden. I bought some cheap generic potting soil at Walmart and it's very heavy and sandy. Which got me thinking, I wonder if it would sink to the bottom and go into my aquarium substrate? I put some in a glass and rinsed it a few times to get rid of those little white things they put in there (can't remember what that's called...) and then filled the glass to let it sit. It pretty much all settled, leaving me with surprisingly clear water. So I'm thinking I may try that in a tank. Anyone tried something like that?