Sand is not magic. It's just a pile of crushed up calcium carbonate. It doesn't do tricks, it doesn't clean your tank, it doesn't "work", it just lays there doing pretty much nothing. It doesn't matter how deep or shallow it is. It's still just a pile of calcium carbonate on the bottom of the tank.
Unfortunately, Ron Shemik and his disciples have been brought up in this thread. As if what they say is true, or actually works the way they describe it. It does not.
The only reason these people have not been brought up on animal cruelty charges is because there are no laws protecting fish and invertebrates from acts of cruelty.
Take any "higher" life form, like a dog, put it in a small enclosure, don't clean the bottom of that enclosure, allow its waste to accumulate to the point that is supports hundreds of thousands of worms/insects/poo eaters/"infauna", maybe even buy some fishing worms to boost the biodiversity, and see what happens. Something tells me you wouldn't get very far by telling the judge that you didn't clean up after the dog because you had flies, maggots, worms, and other critters doing if for you. The dog is likely to get sick and eventually die due to the fact that it was forced to live in a small enclosure with its own filth. This is the exact same thing we see over and over and over and over again in systems like Shemik describes.
When hobbyists started noticing that their animals were dying, these people had to come up with some excuse to explain it, other than the truth which would be by saying, "My method is crap. Sorry for your loss." So, they invented "old tank syndrome". There is no such thing as
old tank syndrome. It should be called
dirty tank syndrome. Clean tanks simply do not have this problem. This problem only arises when we do not clean up after our pets. Like Shemik advises.
For some people, their "belief" in this DSB method is so strong that they'll repeatedly watch their animals die, only to replace them and watch them die all over again. Borenman's personal tank crashed countless times, yet he continued to go right back to the Shemik DSB that caused it in the first place. He even wrote an article about how he disturbed his sand bed and killed all, or most, of his corals. The lesson he learned was to not disturb that six inch pile of rot and filth on the bottom of his tank, because it can kill his corals. That's absurd!!!!:wildone: If I disturb a rattle snake in my living room and get bit, the lesson I learn will not be to tippy toe around the snake so I don't disturb it again. I would
remove the snake from my living room so I don't have to worry about disturbing it again. If Borneman would have simply
removed the six inch pile of rot and filth from the bottom of his tank, he wouldn't have had to worry about animals dying because he disturbed it.
So basically, we can have sand of what ever depth we like, or what ever depth we think our pets may appreciate. We simply need to keep it clean. We wouldn't force any other animal to live under the conditions of a Shemik DSB system, so why would we do this to some of the most environmentally sensitive organisms on the planet?
Peace

EC