I wanted to add DE to "enhance" my filtration. I seem to have a problem filtering all the pollen (green powder) and dead algae (white powder) during spring startup. My water was cloudy. I popped the top on my sand filter this past weekend and the sand seems good - fine and smooth, no channeling, no gunk or clumps. It was about 2 inches lower than the fill level for when the tanks starts curving in. I figured that was fine.

I added 1 1/2 cups of DE to my sand filter. PSI went up 1 PSI as expected. I immediately watched the outlets to see if any of the DE "white powder" came flying out. Previously, I could always see the water coming out from my outlets jets. I could see barley discernible underwater stream of water that I always thought showed small air bubbles or the turbidity of the slightly cloudy water. One minute after I added the DE the water was so clear that I could no longer tell that water was coming out of my jets! (except for where it rippled the surface of the water). I vacuumed my pool, PSI went up 5 more PSI, I backwashed and then added the same amount of DE again. Pump PSI stays stable at +1 PSI over normal and the water is crystal clear - it looks "polished"!

I think I will continue to use DE in my sand filter.
I plan next to add salt and borax to my BBB pool for those enhancement effects.