Sand bed maintenance in a nano?

[mrhasan]

Originally Posted by Koleswrath

I'd recommend at least stirring up and siphoning out the detritus with water changes. Sandbeds will be able to buffer against a certain amount of decay but only up to a point. Eventually a calcium carbonate sandbed will lose it's ability to adsorb nutrients and will need to be replaced. Cleaning it out will help extend the useful life of it.
Greg

Can you please refer me to a link where this claim is justified/proved? I never heard of sand bed buffering/has the ability to buffer/absorb nutrients......