So, I always had 2-3 minor spots where hair algae was quite happily growing, not a major thing though. Since I am using the Deltec FR 509 I noticed the hair algae dying slowly. I was using SeaGel in the inMedia rack, but since I am using it in one of the Deltecs it seems to be way more effective. I have one Tunze post-filter filled with Purigen on the return outlet where it gets pretty nicely swirled around.
Having the inMedia rack surely helps using filter medias as Carbon, Purigen and such, but I think not in the best effective way at all. When I replaced my filter system with the sump, skimmer and so on, I opened one bag of Purigen from the media rack. Only the outer surface of the Purigen changed color, inside, pure white, after about 2 months! Very ineffective way to use such medias then IMHO. Besides, the classical way of filtration should always be mechanical filtration, skimmer, biological/chemical filtration, back to tank.
Another thing I noticed while switching from those Wonderbags to the Tunze post-filter, first the Tunze post-filters are easier to clean and don't clogged that fast. Second, abit more fine debris gets through to the skimmer and this seems to help to create a more thicker foam. Sure, the Wonderbags will do their job, but I think you need a complete set for 7 days if you have to change them almost daily and having a reserve you can throw into the washing machine. Another thing I am not to keen about even if you just wash them without detergent. Imagine how much chemical stuff is still stuck in your washer!