I have one and a sand filter and I do not use DE. Instead I use Slime bag. As JVTrain pointed out helps filter faster during SLAM, I also use intermittently as I think it it adds additional sparkle to water ( but that is subjective). But again if I used a little DE it may filter similarly. Company was good to me quick service, I had no problem with parts nice system all set up. Maybe a bit on expensive side. Can do the same with diesel fuel filter bags which is the basic slime bag but slime bag is modified and nicely sewn so the opening fits 1.5" PVC return. Do a search for slime bag or Duda diesel on this site. A person self modified a bag and I think I like his mod better as you can turn it inside out to clean it.
The slime bag I have filters to one micron, I think I read sand filters will filter to about 10 microns but not real sure of that.