Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
How fine is Silver Sand? I have heard of it, but it is not available here under that name.
If the tank is well planted, roots spreading all over in the sand do not disturb it deep down. Skim the siphon over the surface enough to pick up the large debris.
If the tank has plants that are growing on driftwood or rock, few or no roots in the sand then I would deep vacuum the sand.
Here is why:
Roots of healthy plants will add oxygen to the substrate. This is very good. Keeps a balance of bacteria that are more of the oxygen types, less of the anaerobic ones.
If there are no roots or very few, or if the plants are not doing well there is less oxygen getting added to the sand.
If the sand is deep, or very fine the water does not circulate through it very well, and low oxygen conditions take over. The bacteria that grow in that sort of substrate can produce toxins that may kill the fish.