Just some info...Kitty litter is montmorillonite clay or bentonite clay. It can come in two forms either calcium or sodium. Cheap kitty litter is usually sodium and can form a real clumpy, gooey mess. It's capable of holding something like 20 times it's dry weight in moisture.
The calcium holds it shape/texture and is used to line mud ponds to hold water. The calcium one is also used regularly in the koi hobby to add minerial and trace elements to the water.
More useless info