I agree. I had a Spiny and used sand as a substrate in his aquarium. He spent all day digging around in it. Makes it more difficult to clean the tank, but I think its worth it. Just be sure to wash the sand well before putting it into the tank, otherwise your going to have a mess. Also, you may want to put something over the inlet of your filter. Sand is known to eat the motors of filters up. I just used a piece of pantyhose that I rubberbanded around the intake.

-Chris
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Currently in the US Navy so I have sold off my collection. But over the years I have had dozens of turtles, fish, geckos, and other lizards. Cant wait to get back in the hobby once im out though!