I think you may have picked up the wrong litter; Walmart carries several products called 'Special Kitty'. The one that folks seem to have the most success with comes in a 25 pound red bag.
I use Montmorillonite clay substrates but personally I'm not a big fan of kitty litter; the tan color just don't look natural to me. I've used Soilmaster Select Charcoal (discontinued) and Turface Pro League Grey (discontinued) and currently I have been using Safe-T-Sorb #7941 in my planted tanks. It has a nice natural color, a variety of grain sizes, and plants root well in it. It is dusty and requires a good cleaning prior to first using it. I ordered mine through WW Grainger and it cost me $9.38 per 40# bag and I had to pick it up. It is also available online at Drillspot for $9.29 per 40# bag with free 3-day shipping included. A 40# bag will provide a 2"+ layer of substrate for about six (6) square feet of area.
Here is a picture of my 10 gallon, with Safe-T-Sorb substrate. This tank has no CO2, just Flourish Comprehensive and Flourish Excel. The baby Corys have been in there for over 3 months and have doubled in size.
Last edited by Seattle_Aquarist; 01-16-2013 at 02:43 PM.