[Hornet]

I just got some "mineral clay" kitty litter from the pet shop, just to have a crack at mixing clay for a clay back ground. Obviously not the correct type as it is rock hard and most of the bits wont do anything in the water, just clouded it up a bit. Here in aus we dont have the brands you do over there. What should i be looking for next time i buy some?

 

[afterdark]

100% bentonite clay. Unscented. No additives of any kind and you should be good to go.

Alternatively, you can try a pottery supply shop. There you'd be looking for powdered clay - I bought Sodium Bentonite and RedArt clay - both in very fine powder form. It was very easy to work with.

 

[Pumilo]

Try this recipe. It is much better than kitty litter. The sodium bentonite in kitty litter expands and contracts too much. http://www.dendroboard.com/forum/members-frogs-vivariums/60340-my-first-clay-backgrounds-4.html
You should also read this http://www.dendroboard.com/forum/parts-construction/59903-clay-fail.html Pay attentions to Ed's posts about bio-films.

 

[fishman9809]

Sadly I had this problem too. This happens with cheap kitty litter when the makers heat the clay too hot. Instead of drying it becomes fired clay, making it useless as a litter and as a background. I'm not saying the more expensive the better, but in my case it was. I bought a 25 lb bag for $3 and I got your result. When I got a 15 lb bag of Dr. Elsey's Natural Cat Litter for $10 it worked flawlessly.