Help - major algae now cloudy pool

[waterbear]

Hmmmm, this "change the sand" issue has me puzzled.

Matt4x4 and others here are advocates of doing so, but I've never understood the logic. In fact, many of us think "old" Sand may filter even better than new. (I'm not so sure about that one but it's logic has some merit)


Dave S.

This issue I wonder about. Have never used a sand filter in a pool but have used sand as a mechanical filter medium in large aquariums. General concensus there is that the constant flowing of the water over the sand erodes the facets off the silica crystals and rounds and polishes them. It is believed that this leads to channeling and increases the minimum particle size that can be filtered by the medium making it less effecient. Don't know if the same factors will apply in a pool filter but I suspect they might. Anyone have some info either way? I am curious about the logic of not changing the sand. Why do you think old sand may filter better than new? (by the way, this info is not "fish stored"
because there are very few commercial sand filters for aquarums and most aquarists build their own)