thanks for the picture. can this be added to a HOB filter? how?Yes, those are ones you are in rolls. Great to layer on drip trays and cut able patterns. I just use the loose ones in a bag. About $3- $4 per bag as shown. This is what I place in my baskets for my fx5 canister.
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Also anyone else think it's ironic that it's called "poly fil" tehe.