Building a Larger Pond Filtration System.

Previously, I had created a page that showed our pond filtration system (now deleted.). It was simplistic and we were so sure it could handle the large amount of water passing through it and up to the waterfall.

Our Pond Problems

It seemed to work well for the first year and even part way through the second year, but now in year three, the system was failing to properly filter all of the sub particles. While we did finally cut down many of the half dead and just plain old oak trees, we also have very tall evergreens surrounding our smaller pond.

This spring we experienced brown foam to sludge floating on the surface of the smaller pond. It is the smaller pond that contains the intake and filter system, so all of the water from the larger pond makes its way from the waterfall, to down the stream and into the smaller pond.

In completing my research, the brown foam, which can also present itself looking like an oil slick, is actually pollen from our evergreens. If standing in the right location and witnessing a wind gust, you can actually see the pollen fly off the trees. Naturally, the pollen falls to the surface of the pond.

And let’s not forget about the dry needles falling from the trees. Once on the pond, the particles float towards the filter intake.

I’m sure quite sure that in the previous two years we had pollen and needles, it just took hold of the pond in year three.

Start From the Very Beginning

A mistake that we made from the very beginning is not cutting down the old building-pond-the-loop-chicagosickly oaks prior to building the pond. During the very first fall season (2008), thousands upon thousands of leaves fell into the pond. I tried desperately to scoop up as many leaves as I could before the snow fell, but many leaves became saturated and sunk to the bottom of the pond.
The following spring (year two), it was quite the task cleaning out the soggy leaves and acorns. Naturally, many leaves were missed only to be left fermenting and causing unnecessary gases within the water. While the water did not turn brown, the clarity did change. I believe that many pond owners use netting in the fall and cover their pond(s). This is a good idea if the pond is medium to small in size.

Draining the Pond

In retrospect, I now think that we should have drained both ponds, cleaned out the leaves and re-filled with fresh water.
In year three we did cut down many if not all of the old oaks that were close to the ponds and we drained the smaller pond, cleaned it out and proceeded to build a new filtration system.
During the cutting and the cleaning, we also scoured our garden centers looking for a filtration system that could handle the 16,000 gallons of water contained in both of our ponds. No success. We decided to do it the old fashioned way by building a pond filtration unit with a small deck for seating pleasure.
How did we calculate our water volume? Multiply the width x length x depth x 7.48 = water volume, or go here.

How the Unit Was Built

The filter box, which was built from preserved wood (the dimensions can be pond size appropriate). The completed box was placed on a ledge within the small pond (which we drained). As seen, the box should be level when put in place.

At the one end are 3 output hoses. Only 2 hoses are currently in use. The 3rd hose is a ‘just in case we need it’ hose. We augured 3 – 1 1/2 inch holes. In each hole we put in a 1 1/2 inch grey PVC grey fitting.

Once the fittings were caulked in place, we inserted the 1 1/2 inch flexible ID (interior dimension) hose and held the hose in place with a 1 3/4 inch stainless clamp. These 3 hoses run from the pond’s edge approximately 50 feet underground to the top of the waterfall. Once the pond was re-filled with water, and before the hoses run underground, we covered the exposed 3 hoses with larger stones. Inside the box in front of the 3 hoses we placed a coarse filter media mat. This is an optional step, but I wanted to make sure that when I took out the other two filter media mats to clean, larger objects would not pass through the hoses and clog the pump.

Above the 3 hoses is the water intake area.

Resting flat inside the box, above the 3 hoses and just below the intake area, are the two filter media mats. To hold the filter mats we built a framed screen. On top of the screen we placed a fine media filter mat. Next, on top of the fine mat we placed a coarse media filter mat.

Ergo, when the water flows into the large intake area it passes through the coarse filter media mat, then the fine media mat. Even the framed screen holding the media mats helps filter small particles. The two filter mats are easily removed and rinsed with a garden hose once a week. Once a month we turn off the pump and remove the filter mat that we placed in front of the 3 hoses and rinse it clean with the garden hose.


Filter media mats can be purchased at any garden center (supplying pond products) or online. In our case, I had to cut the purchased mats to fit the area of the framed screen (2ft in length by 1 ft wide).

Another element for keeping pond water clear is the use of activated charcoal (in a mesh bag) and bio-media stones (in a mesh bag). I place the stones inside the filtration box close to the intake area. The water passes through the bio-media stones and helps colonize and hold onto the beneficial bacteria.


Bacteria are essential for pond health. A product that I use to add beneficial microbes and enzymes to aid in reducing sludge is called AquaClearer by EcoSystems. When used as directed, it naturally helps to clarify pond water. This product also contains part activated charcoal powder. While we do not have fish in our pond, this product is safe for fish and plants.
Did you know that barley also helps to clear pond water?

Using Barley

Many golf courses throw a bale of barley into their pond’s mid-section (deepest area) to maintain water clarity and health (miniature barley squares are also available for smaller ponds). The barley is replaced every few months depending on the weather conditions. The hotter the conditions, the more frequent the bales need replacing.

Barley can also be purchased in pellet form and liquid. The first two forms are slow to act and will take a few weeks to clear a pond; however the liquid form works immediately and is obviously the most expensive of the three. My suggestion is to use the product prior to any pond water issues. Be proactive, rather than reactive.

We chose to place a bistro set on the deck area and planted garden daisies, a Virginia Creeper Vine and an Astilbe Koln perennial.

UPDATE: Due to the fact that I replaced the larger pond with a sunken garden, the above filtration system is no longer operational. The stream no longer exists and has been replaced by a mini waterfall and pump.

Final Remarks

I will be adding additional comments to this page on how well (or not) this new filtration system works. Our ponds have been a challenge this year, but I have learned many valuable lessons, which I have passed along on this page. Most importantly…be proactive…keep your pond balance healthy. We have a Caribbean paradise in our backyard. Sitting around the camp fire and listening to the sound of water lapping up against the boulders. We like watching the water cascade down from our 10 foot high waterfall. Oh yes, I almost forgot, watching the ducks) swimming almost every morning at 6:15.

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