I used a rubber sheet cut to fit behind the flange with the hole for the pipe barely large enough to fit snugly around the pipe. Most people cut an X smaller than the pipe diameter since the rubber will stretch to fit. I used a silicon type adhesive/filler to attach this gasket to the filter body although there are a number of products that would work as well. It doesn't have to dry hard. In fact it is better if it remains flexible. It has been in place over 10 years now. The flange can be tightened down to compress the rubber to prevent leaks. Check the plumbing section for DIY rubber sheets. They are usually about 4x4 inches.

Check your 'in' tube. I have been having issues with string algae building up right where the water should be entering the bio filter. I have been taking care to clean that area every week when I change my filters. You may be getting good flow for a brief time, as you turn off the pump. If there is a buildup it may dislodge itself when the pressure of the water pushing on it stops. Then when the water flow begins again, it plugs up. Good luck.

We clueless have to stick together! :) OK, people -- the water was stink-o-rama the first two days. Now it is very mildly pond-ish, not so bad. The only "rotten" scent is exactly at the filter. But why are there so many bubbles now? Water possibly LESS clear now because the movement is so strong. Waiting to see what happens after a couple weeks. Anything else I should be doing??

The bio filter I made from a new plastic paint bucket and lid loooks just like Jeffs, miinus the airpump inlet. But I have a problem I hope someone can help me with. In order for the water to flow out into the pond, the bucket must be several feet above the pond. So to conceal the bucket I will have to build the rocks a lot taller than I would like. Seems like the pump will pump the water to the bucket, but hasn't got enough umph to push it up-hill through the tubing to the 'falls'. I would like my bucket to be on the ground, (just above the pond), and have the water run up the tubing to the top of the rocks. This way I won't have to built a 3 ft. tall wall to hide the bucket. Another question. Do I need a lid on the bio filter? If I made a wider, lined, box, could I leave it open, or must it be closed to work? Seems like I remember seeing one like this when I researched construction of a bio filter on Garden Wed a few years ago, but can't find it now.