Building and calculating an upflow bog with EcoBlox

We recently received a question on a previous blog: BOG FILTRATION, THE PERFECT COMPLEMENT TO BIOLOGICAL FILTERS. The question was:

Do you have any additional information about building and calculating an upflow bog with EcoBlox, like shown in the graphic at the end of this blog post? You already talked a bit about the surface area of the bog compared to the pond but what about the depth and the number of blocks stacked on each other for example? 
I want to build a 15′ x 13′ pond with 3000 gallons and 9′ stream. Pond will be filled with stones and gravel, some plants and 20 goldfish (around 8″). How many blocks do I need and how do I arrange them for a fitting surface area of the filter? Do you have any recommended product to be used as tube under the blocks? Or do I have to build one myself? If so, do you have any instructions to do this?

Great question O Noble Ponderer!

Bogs are sized by surface area. 10% of the area of the pond in bog area is sufficient to consume all the nitrates a goldfish pond is likely to produce. At the other end of the scale are Koi, which need three times as much area, 30%, planted to bogs.

With 205 square feet of pond, 20 square feet of planted gravel will be sufficient. You have a 9’ stream, which simplifies matters greatly. What I would do is set one or two Eco-Blox at the top of the stream, on the existing grade on top of the stream liner. I would install two 2” or 3” flanges or bulkhead fittings on either side of the chamber thus created, down low so water enters and exits the Eco-Blox near the bottom of the block. On one side I’d attach the pipe from the pump, on the other a drain valve. Take a look at the sketch.

Water comes from the skimmer into the Eco-Blox on one side, flows up and out through a 4-6” layer of ¾-1” gravel on top planted to various low grasses or other aquatic plants, which are also planted in the gravel of the stream. The Eco-Blox under the gravel acts as a settling chamber. The outlet on the side opposite the inlet is valved. The valve is buried near the flange or bulkhead fitting, attached to a piece of pipe out to daylight somewhere.

I usually just set an 18” length of 4” pipe vertically over the valve so the handle can be accessed periodically to drain out the muck which will accumulate in the chamber. If I can’t reach the valve with my hand, I’ll slot the end of a pipe to create a wrench to turn the handle. This is necessary usually only once or twice a year.

You’ll have a great little active bog filter that uses the top of Eco-Blox chamber plus the stream to provide the necessary area for plantings. Plus a built-in settling chamber that will remove much of the suspended organic debris constantly and automatically. You may also consider adding a bottom drain to the skimmer, to pick up the rest of the debris. But that’s the subject of another post.

How Many Eco-Blox do I need for my Pond-free Feature?

Pond-free System

Pond-free features, where a pond or waterfall recirculates from an underground reservoir, have become very popular because they are easier to build and maintain than fish ponds. The Pond-free basin is a hole lined with EPDM rubber to make it waterproof, filled with water matrix boxes called Eco-Blox that can support thousands of pounds.

This weight-bearing reservoir can be hidden under gravel, lawn, pavers – you can even build waterfalls right on top of it! The water in Eco-Blox basins stays clean and clear, so maintenance is much simpler. Pond-free water features are generally safer too, because there’s no way for anyone to fall in.

With the great popularity of these features,  we receive many questions. One of the main questions we get at Atlantic is “How many Eco-Blox do I need?”

Here’s how to figure that out.

First, find the volume of water needed to fill the stream and falls to overflowing.

Usually about 3” in the whole stream will do. Measuring everything in feet makes things easier, so convert 3” to a quarter of a foot. For a 6-foot by 2-foot stream:

Length x Width x 0.25 feet = 6’ x 2’ x 0.25’ = 3 cubic feet

We’ll want 3 times as much water in the reservoir as we need, so the level will only drop by a third when we turn the system on before it starts recirculating:

3 cubic feet x 3 = 9 cubic foot reservoir

Finally, we’ll divide by 4.3 cubic feet, the number of cubic feet in an Eco-Blox:

9 cubic feet ÷ 4.3 cubic feet/Eco-Blox = 2.1 Eco-Blox

With the addition of a Pump Vault to house and protect the pump, as well as providing a little extra water volume, 2 Eco-Blox will be perfect!


Now that you know how many Eco-Blox you’ll need for your next project, check out our video on how assemble one.

 About the Author:
Demi is the Direct of Product Information for Atlantic Water GardensDEMI FORTUNA

Demi has been in water garden construction since 1986. As Atlantic’s Director of Product Information, if he’s not building water features, he’s writing or talking about them. If you have a design or construction question, he’s the one to ask.