I have a 29 gal. tank and was considering the CPR Bak Pak 2. Is there a cheaper skimmer that will work as well on my tank? Not that $130 is expensive, but just money is money. Also do I need the one with the Bio Bale? I have a Aquaclear HOB and live rock(1.5 lbs per gallon) Also, has anyone ordered off ebay? Pros and cons? TIA!