After reading that kitty litter has iron in it, I did some more research on kitty litter and found this info at
http://www.thekrib.com/Plants/Fertil...at-litter.html.
Date: Mon, 19 Jun 2000
In my 55 gallon with almost exclusively kitty litter that plant roots penetrate eagerly. I have a friend with a 125 gallon all kitty litter substrate with 1.5 inches "gravel" on top. He had to tear it down when he moved. The plants had grown so well that the substrate was almost one large mass of roots!!! I've noticed in my kitty litter substrates that the 'soil' is actually not very compact. In fact it seems to be almost in a state of suspension. It woldn't take much water flow to greatly disturb it. However I also notice the roots on the side of the aquarium (looking through the glass) growing very well, especially with my Glosso which has rapidly grown through the 1.5 inch of "play sand" into the kitty litter. This glosso, from several 'sprigs' has grown into a virtual carpet in only 4 months. And I haven't added any CO2!!! I love my kitty litter substrate!!!
by WEREED5518/aol.com Eric
Date: Tue, 16 Feb 1999
After testing pH's, I narrowed it down to STP Oil-dri and Special Kitty litter (Wal-Mart brand in red bag). Special Kitty pH of 1 tsp/cup water, swirled, allowed to settle was 6.5.
by "Jamie Johnson" <jjohnson/davisfloyd.com>
Since replanting can cause some litter come up I am going to add it to the top soil I am using. I will top it with flourite. I have to test flourite's ability to keep the dirt down before I decide if I am going to need to use some sand on top.