Take a look at this link. This guy did some intresting stuff with barrels and there is even a diagram! I prefere K1 as bio media since there is lots of air, it's self cleaning and keeps my parameters in great shape. I recently posted a filter I made myself, works on the Bakki shower and Easy principle. It might fancy your intrest and it's pretty low maintaince. The key to good bio filtration is low maintance. You don't want to desturb the bio bed to clean it each time. Good luck!
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