<a href=showthread.php?s=&postid=6476824#post6476824 target=_blank>Originally posted</a> by barryhc
"Worthless" is a HUGE word.
Sand beds get a lot more Advection ( bulk ) floe when they have a layer of .5 to 1.5mm sand at the top, and with the much larger flow that this allows.
I sure do like the animals, I'm going to keep them in my tank.
> barryhc![]()
Diffusion, in its technical sense, is a very slow process. Even single-celled creatures such as Paramecium cannot depend on diffusion to move compounds throughout the cell and have developed internal circulation organs, etc, so that they need not depend on it. Ruppert's book "Invertebrate Zoology: An Evolutionary Approach" has a chapter on protists that discusses some of these mechanisms.
So I think the bottom line is that hoping diffusion will do the job is very iffy, to say the least.
The problem with grains of sand in the range you mentioned is that a lot of the sandbed animals need a finer substrate. Your approach will prove more bulk flow; a DSB is designed to depend on bioturbation. I've used the coarser substrates and not liked the results.