First post from a budding planted tanker here.
TL;DR: Stupid Kitty litter dissolves into mud. Plants and fish love it. Pics incoming.
I read that Special Kitty All Natural Unscented Nonclumping from Walmart (hereafter called "the litter") was good, and like an idiot I didn't test my own purchase before scaping a 29G with special kitty capped with Fluval Stratum. Unlike every experience with the litter on the net, I noticed a distinct scent (the jug LIES!) and as soon as I added water the litter turned into a fine white mud instantly. However my 400gph filter cleared up the water overnight, and with a few stems and ~30 watts of daylight fluorescent, (one T8 and one CFL) I added livestock in 24 hours. Obviously I seeded the filter with well-aged mulmy media from a 55G, but testing and my perky Endlers fry showed zero cycle and no ammonia spike
Anyway, I was concerned about the effects of the mud below the Stratum, but after a month or two the stems are now exploding with growth in the high-light areas the tank. No black brush or green hair algae on any leaves or glass, and only a couple spots of the green spot algae. Endlers, Platys, red cherry shrimp, ramshorn and pond snails all thriving in a heavily overfed kitty litter tank and it still shows zero nitrates two weeks after a 30% water change.
I had been worried my first post might be a tragic failure of the litter, but as long as I don't stick my finger in the substrate, the litter stays under the Stratum cap. I should note I deliberately did not move malaysian trumpet snails over from my 55 because I didn't want mixing in my substrate. Vigorous root growth is visible in the litter layer, and fish waste clearly falls through the Stratum to reach the interface. I haven't done a full water parameter test yet, but preliminary quick-strip tests put hardness and pH in normal expected ranges for Seattle tapwater treated with Prime.
Just wanted to add my experience with this particular combination (and my first real planted tank). Pictures will come soon if anyone cares.