I use a milk crate full of lava rock around my submersible pump and it
works great.

bk wrote:
We have a Beckett pump and Tetra PF3 filter. The pump runs like a champ, but
allows debris to pass thru. Unfortunitly the filter catches this stuff
before it passes intot he actual filter. This causes clogging and a great
reduction of flow rate. I'm cleaning the filter connection at least once a
week. I need a way to prefilter the pump. This pump is about a 1200 gpm.