I personally have and like the inTank mediabasket. In my basket, I have purigen on the top shelf, chaeto with a submersible light in the 2nd chamber, and rubble rock in chamber 3. With this setup, have had no issues with chaeto blocking the return pump intake.
If you don't have a media basket, buy enough rubble rock to have about 2-3 inches in the bottom of chamber 2. This acts and a screen for the chaeto and a live filter(you can add something like Microbacter to help it start). I know people with BC14's here locally that run just rubble rock and have enough live filtration that they don't need anything else.
IMO, not having the sponge is a good thing as you don't have to remove and clean it periodically. Replace it a bag of Chemi-pure Elite.