You absolutely do not need chambers to direct the flow of water through the biomedia. Its a falsehood. I love poret foam but the beauty of a sump is ease of maintenance. Since you have sock holders the poret foam will just be some unnecessary maintenance. You can use a tee and create two draines and add another sock holder to create more mech. Order 10 or 15 200 micron socks from mcmaster carr. Rotate clea ns socks with dirty. Once a month throw the dirties in the wash machine