Originally Posted by azfishgal
I did read somewhere here that to be true, but havn't found the answer as to why or what can happen. I had mentioned having a 3" sand base, but was told the same thing (without explaining why). So I'll dig a little deeper and see what's up with that. I want sand sifting creatures, so I'm thinking 4" (boy that's a lot of sand!)
In a nut shell:
Sand beds have been known to "fail". A shallow sand bed allows for critters to clean sand. A deep sand bed allows for anearobic (oxygen poor) bacteria to break down nitrate into nitrogen and oxygen gasses. A mid depth sand bed tends to become a wasteland. Too deep for critters, not deep enough to be oxygen poor.
Avoid sand "sifting" creatures (such as certain stars, horseshoe crabs, etc.)for a healthy sand bed. They eat your beneficial worms, pods, etc. and then can starve. Burrowing creatures (sand shifters) are fine.