I just bought a NIB Marineland Magnum 350 PRO for $50 out the door. Gotta love one base stores have 75% off sales on stuff they're never going to sell.
It basicly replaces the carbon cannister thing with a piece of pvc with lots of holes drilled in it, then a piece of poret faom slides over the pvc. Its a genius design. I had to clean my 350 every 5 days or so before, now I only change it every 2 months or so. There is hardly a decrease in flow.
http://www.plecocaves.com/Poret.htm
^^^this is the link to the poret kit, or you can build it yourself, but for $30 shipped it was well worth it imo. Not quite as good as the micron filters, but a lot Better and cheaper in the long run.
Thanks for the clarification. I'm definitely setting this up. Can I still run carbon in the PVC tube?