Be very careful
Pool filter DE is very, very bad for your lungs.
Wear a mask when you are dealing with it, do not open it in the house, do not open it in a windy place.
I used to use it instead of the more expensive garden DE which is used to deter slugs, but there is a difference in how it is milled in that the milling process actually makes it much sharper and dangerous if inhaled. It is very bad for your lungs. I began to notice some breathing problems after working where the DE had been used. Eventually I just bought the expensive kind and threw the other out.