There are a few of the biotope substrates available like Eco complete and Seachem where the substrates contain Flourite which is good for plants and usually has clay within them.. Another good plant species would be cryptocoryne wendtii i love this plant and in my opinion is far better than Amazon swords..
I haven't personally used cat litter but i hear it is great for planted aquariums just make sure you get the non scented and 100% clay cat litter with no chemicals, make sure you use it as a first layer and then place the intended gravel over it..
I haven't personally used cat litter but i hear it is great for planted aquariums just make sure you get the non scented and 100% clay cat litter with no chemicals, make sure you use it as a first layer and then place the intended gravel over it..