DIY Submerged/Underwater Biological and Mechanical Pond Filter. IMPORTANT NOTICE: after running this filter for a couple of months, I did find a design fault. The filter was sucking in air, which was present in the water. Because I only drilled relatively small holes in the lid, the air could not escape because the pump was constantly sucking water in. The top of filter would eventually fill up with air and float to the surface of the pond. To combat this problem, I drilled several more small holes and 4 large ones roughly 2 inches in diameter in the top of the lid. Everything is now fine and any air which does get sucked in by the filter can now freely escape through the larger holes.
How to make a simple but efficient HOME MADE/DO-IT-YOURSELF biological and mechanical underwater pond filter that will help keep your pond healthy and free of potentially lethal pollutants that are produced by fish waste.
To make this filter you will need the following items:
A suitable pond pump that can pump the entire volume of your pond water around at least every once every 2-3 hours.
A bucket/bin or container with a sealable lid. (The one I'm using is a 25 L fermentation bucket).
A drill and appropriate drill bits to drill holes in the top of the lid.
Filter material - plastic rings and sponges etc.
A brick or 2 to place in the bottom to help weight down the container , especially if the filter material you are using is buoyant.
PVC waste pipe that will fit your pond pump. (I purchased a 2 m long 22 mm waste pipe at about £1.50 from a well-known DIY store).
PVC 90Deg Tee that will go on the top of the straight pipe once you cut it to your desired height.
A saw to cut the pipe.
You will obviously as need a pond and a flat base to place the submerged filter on.
Depending on the size of the container you use, you also need to make sure the pond is deep enough that it covers the container by at least 5 inches.
This particular filter is very useful for raised wooden or brick ponds as the filter is hidden inside the pond and you don't have to have an ugly external plastic one to look at. My pond is about 350 gallons and this filter (25 L bucket) should be suitable for anything up to 500 gallons, or a little bit more. I currently have around 12 medium to very large goldfish of different varieties and they all seem very happy and healthy with this filter setup.
The filter works by sucking in water from the top of the container via the pond pump in the bottom. The water is drawn through the filter material where friendly bacteria will colonise the filter media and convert the nasty chemicals into less harmful ones. The filter will also work mechanically and remove some small particles. Despite many YouTube videos claiming biological filters eliminate green water (algae) they will not do this by themselves. You need to make sure you have a well planted pond with plenty of oxygenating and surface plants to mop up nutrients and provide shade.
Tags: DIY Submerged/Underwater Biological and Mechanical Pond Filter, DIY, Pond Filter, BIO Filter, Pond Fish