I purchased the tunze 9004 DC unit and placed it in the far right rear chamber (of aio) figuring this would be the best placement, but I cannot get it to produce any foam. I realize it being placed in this chamber it will not do any surface skimming other than what is being skimmed from the tank into this chamber, but I don't think that has any bearing on this issue. The unit has been running for roughly 4 days now. It's producing plenty of foam, see the picture. How are you using your tunze unit in your aio? where do you have yours placed?