Please help, I think I'm going to go crazy if I don't figure this out. Whether I use eco earth, or cypress mulch, or a mix of sand and soil and peat moss as the substrate, I must be looking at this wrong because 9 inches deep in a 4by8 enclosure seems to be about 24 cubic feet and eco earth (for example) is about $34 for 48 quarts and at that rate it would be hundreds of dollars to get 24 cubic feet! I must be doing the math wrong! So, to boil it down to its simplest terms - how many bags of a 48 quart bag will I need for a 4 by 8 enclosure? Also, and I know I'm opening a can of worms, but would eco earth be good for a tegu or should I go with something else? Thanks for any help you might be able to send my way!