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Of all the pond devices that you’ll see used in a small pond, few have ever been reinvented or replicated as much as a pond filter in the DIY realm. DIY of course stands for do-it-yourself and the relatively simple design of most biological pond filters easily lend themselves to someone who wants to build one from scratch.
The purpose of any pond filter is to help remove physical and elemental contaminants from the water. For instance pieces of leaf debris or single cell algae particles would be considered physical in nature. Elemental substances by our definition would include things like ammonia or nitrites that are created from the breakdown of fish waste. The reduction and elimination of these is very important because they are toxic to fish.
Pond filters in a broad sense, come in two varieties. Some may be physical filters only. Like an oil filter in your car, for example, these are simply designed to take out some of the larger particles of stuff that are floating in the water. This debris gets caught in the mesh or foam, and filtered water is allowed to pass through. Many very small ponds, and those without fish, may use these and they can be helpful at keeping a pond cleaner.
Pond Bio-filters And How They Work
A more powerful, and we think, useful pond filter is the biological filter. This particular filter may or may not have a mechanical pre-filter included in it, but within a bio-filter is material that will grab some of the organic debris that passes through it. The important part though is what’s also inside the filter. The “biological” component is actually beneficial pond bacteria and this is the real cleaning tool of the device.
As material gets trapped, and this is specifically relating to organic material, this will be broken down, or in a sense, eaten by the bacteria. These good bugs will also convert ammonia and nitrites into harmless nitrates which is very important work for fish ponds.
Of course, there are many commercial varieties of pond filters available and many of them are very good. Some, such as the fully enclosed bead filters can be quite expensive which is one of the reasons why many people want to save money and try to do something for themselves.
Here’s a video showing a very good, basic design for a gravity-fed pond filter, with an equally good explanation of how it works. This one uses a plastic storage tub.
DIY Barrel Pond Filters
The barrel filter uses a 55-gallon barrel. Often these are blue in color and can be found quite easily if you know where to look. Many factories and companies use these to hold liquids. Ideally, if you know someplace that uses these for food-grade products rather than chemicals of some kind you’d be better off. What’s nice about the barrels is their holding capacity and they can be found inexpensively. In some cases, you might find them for free but you can also get them on eBay for around $20.
Barrels make good filters because of their round shape. This provides a very nice vortex or circular motion of the water internally which can help add a bit of oxygen to the water prior to it rising into the bio-chamber. Multiple barrels can be daisy-chained together to help provide filtration to bigger ponds.
Pvc pipe is installed internally within the barrel, along with some screen, filter foam or screen for prefiltering, and some type of media that can provide a home to the bacteria. The photograph included here show’s a nicely designed barrel filter in use in a fish holding tank. Water can be pushed into the filter by use of a submerged or external pump, and discharge takes place through an outlet pipe near the top of the barrel.
To get more details on this filter design this is one of the best videos we’ve found online. It discusses how to properly daisy-chain barrels together for higher capacity filtration for larger ponds.
The Skippy Filter
Update: The Skippy Filter website that was maintained for many years is no longer available. Nevertheless, this filter has remained quite popular and you may still use some of the widely available components to build your own filter. I decided to leave the Skippy in the article as it might provide some inspiration for the reader.
Perhaps the most popular DIY pond filter online is called the Skippy filter and this uses a stock tank for the filter body rather than a box or barrel. Stock tanks also provide some circulatory motion of the water much like barrels and they will also have water enter at the bottom of the tank and this will rise up through the filter media, which is made up of numerous brillo like pads that not only filter the water but they also provide a home to the bacteria as well.
Once filtered, the clean water will exit near the top of the tank. In this way, the Skippy filter can serve somewhat like a waterfall filter and it can be hidden behind rocks or plants.
Comparing the various designs you’ll find many similarities. Really the main difference for the Skippy is that it uses no pre-filters or pads, just the loose scratch pads, to filter the water.
One key point that you’ll read about concerning these bio-filters is that they generally don’t require too much cleaning, in fact as the Skippy information will note, you may not want to clean them at all. It’s important to note that both of these designs and really any bio-filter will need to be primed with beneficial bacteria and this is easy to do. Simply add your favorite blend to the pond water and it will circulate into the filter. This may need to be done from time to time to keep bacteria counts up, and it certainly should be done at every spring start-up or following a period of downtime where water flow is not going through the filter.
What About The Filter Media?
Up to now, we’ve talked a lot about what these DIY pond filters look like…but in truth, the real workhorse in this operation is the filter media. That material, be it foam pads, plastic balls, or tubes, no matter the make, its purpose is to provide a sustainable home to beneficial microbes.
It’s the microbes that help to manage nutrients from fish waste or decomposing organic material. They also serve as a natural pond cleaner and balancer, and that work will provide the pond owner with a better-looking, and much healthier pond.
So is there one form of media more preferred than another? Opinions vary because it seems, as in the case with the Skippy filter, many porous materials will work reasonably well. Some of the top-rated media to checkout however would be the K2 Biofilter Media, the Nezo Bio-ceramic blocks, or the Easy Pro Bio-Blo.
Do It Yourself Or Not – It’s OK
The most important thing to remember is that you don’t need any great construction skills to make a good, useful DIY pond filter. With the information resources provided here, you can experiment and learn and ultimately create the perfect filter for your pond.
If after viewing some of the videos you come to conclude that building your own filter is more than you want to tackle, you can still find easy to assemble pond filter kits online. Many are designed to make creating a waterfall or spillway quite easy and they work great as a gravity-fed pond filter.
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