Trialsguy,
Working at Aquatic Eco for a while, I recall that questions several times a week. A sand filter is great for a swimming pool where the water does not contain organic material, (fishwaste, dissolved and solid). The bacteria will grow on the sand grains resulting in a clumping them together. We have seen the grains stuck so well that the backflush method simply created channels opposed to fluidizing (made up word) the sand.
If you were to use the Filter assembly as a holding tank and add a different media like bio balls or foam or lava rock, then you might be okay.
