Around 4½ years ago, I decided to build what I like to call my dream pond. I’d always admired those stunning recreation ponds you see in professional showcases, but the six-figure price tag was way out of my budget. Even the DIY kit versions were too expensive (for me!).
Luckily, I already had a decent understanding of natural filtration, so I set out to create my own filter system — using cheap, easy-to-find materials.
The Budget-Friendly Build
For my large bog filters, I used old plastic drums that once imported olives. This olive drum will sit inside the filter and provide a way to completely drain it. I picked them up for about $10 each.
To evenly disperse the water throughout the bog, I used a trench liner I could special-order from my local hardware store for around $20.
The professional-grade snorkel and centipede units alone would have set me back about $1,000 each. My DIY versions did the same job for a fraction of the price.
Materials I Used:
- Old olive barrels — $10
- Trench liner — $20
- Pond liner
- Nonwoven geotextile fabric (to protect the liner)
- Rock and pebble in different sizes
How a Bog Filter Works
Professionals often call this a wetland filter, but it’s the same principle as any bog filter: bacteria and plants work together to remove nutrients from the water.
Fish waste, leaves, and other organic matter release nutrients that can cause algae blooms. The bacteria and plants in the bog filter process and consume most of these nutrients — provided your filter is sized correctly.
If you’re not sure about sizing, I’ve got a free bog filter calculator (plus a pump flow calculator).
Why I Love This Design
There are a few reasons the professional wetland filter appealed to me:
- It’s built into the ground — easy to disguise for a natural look.
- It’s scalable — you can make it any size you need.
- It’s easy to clean — designed with a drain and flush system.
Instead of paying for the snorkel and centipede units, I made my own:
- Snorkel unit: $10 plastic barrel
- Centipede unit: $20 trench liner (or PVC pipe with drilled holes)
Alternatives if You Can’t Get the Same Materials
Some people overseas can’t source trench liners. No problem — you can use any sturdy structure that will hold the rock and pebble over the dispersal pipe.
If I hadn’t found trench liner, I would have used 150mm (6″) PVC pipe with large drilled holes. The goal is even water distribution and a path for debris to travel to the clean-out point.
Flow, Waste, and Void Space
You want a gentle trickle from the dispersal pipe, not a spray — that way solids settle at the bottom. Professionals often add matrix blocks to slow the flow further and create space for waste to accumulate.
For my pond, I skipped this step because I have small native fish that don’t produce much waste. If I had larger fish, ducks, or turtles, I’d definitely use something like:
- Matrix blocks
- Milk crates
- Plastic pallets
Building the Filter
Here’s the basic process:
- Excavate the hole — with a slight depression for the dispersal pipe and cleanout barrel to sit at the lowest point.
- Install pond liner — add geotextile fabric for protection.
- Fit snorkel and dispersal pipe — angle the pipe slightly towards the cleanout barrel to help waste move during flushing.
- Backfill with graded rock and pebble — larger cobbles near the pipe, smaller pebble towards the top.
- Plant your bog — choose plants suited to your climate and pond design.
Cleaning and Maintenance
When it’s time to clean:
- Place a dirty water pump in the snorkel unit
- Flush the filter surface with pond water
- Let debris settle into the snorkel area
The resulting gunk makes excellent garden fertilizer.
4½ Years Later — Any Regrets?
None at all. The filter is still going strong, the water is crystal clear, and maintenance is minimal. You can build this style of filter:
- Inside your pond
- As a separate filter connected by a stream or waterfall
- Even inside the stream itself
It’s not the only way to filter a pond, but for a natural-looking setup, I reckon it’s the best.
💡 Want to design your own pond without the guesswork?
Check out my free pond calculators and Pond Formulas Blueprint — the exact formulas I use in my builds.