take out the bio bail that stuph can lead to nitraate probs just like bioballs unless you are doing a fish only tank. have had a couple cpr backpacks and have always taken that stuph out. use that area for carbon or phosban.
For the same price, I would bet you would be much happier with this.
I mentioned to you before that I have one of these on my 29g and it's phenomenal.
No pumps in the main tank...pump is in the skimmer itself.