What Exactly Is Pond Filtration?

Pond Filtration Primer

clear pond

Clear water is the goal. Now how do we achieve that?

Probably most of you realize that backyard ponds need filtration. Filtration comes in all sorts of forms however -- maybe not what you have pictured in your mind either!


Submerged Filters

bad old pond filter

Ancient pond filtration. No one wants to see this in the
bottom of their pond!

In the beginning... okay maybe not the beginning, but before modern day pond filtration was invented in the early 1990's, most pond filtration consisted of a pump in the pond bottom which drew the water through a container of lava rock also sitting in the pond bottom. This was somewhat effective, but unsightly and very high maintenance. This system was tweaked a bit to become the submerged filters that are still sold today -- a good percentage of new pond owners start this way, but it hasn't changed that much -- you can still see it in the pond bottom and it's still high maintenance. But for many, this is a low cost way to filter their pond and get started.


Modern Filtration

natural biological pond filter

Today, modern filtration equipment is not
seen at all in or around the pond when
it is installed properly.

Today's modern day filtration consists of two components -- a biological waterfall and a skimmer.

biological waterfall filterfall
This is a biological waterfall, or a filterfall. When properly installed, this filter is completely disguised with a waterfall! 

pond skimmer
Working with the biological waterfall is a skimmer. This is a pump housing. Again, when properly installed, you will not see this skimmer at all.

This system filters the pond exponentially better than the submerged filter, and if installed properly, this filtration system is hidden, making the pond look much more natural.  The biological waterfall cleans and clarifies the water while the skimmer both protects the pump from debris and removes debris from the water. Read more about Biological Waterfalls here. If you want to see this filtration system in action, just look at any of our ponds at our display center -- they all utilize these exact filters!


External Filtration

external pond filter

This spilling urn is both a filter and decorative!

Somewhere in between the submerged filter and the biological waterfall/skimmer combination lies the external filter. While the pump still sits in the pond bottom, the filter sits outside the pond making filter maintenance easier. These filters can be easily hidden or decorative such as the photo above. These filters are a great option for smaller (i.e. less than 800 gallons)
or hard-lined ponds.


There are other natural pond filters in the pond as well. 

Creeks and Streams

stream on pond with waterfall

There IS a stream in there! The plants are thriving!

stream bed mechanical filtration
Look at all the muck built up in this stream bed! Thankfully the stream caught all this junk before it floated into the pond.

Streams (a.k.a. creeks) are great debris filters. And they look so wonderful too! You don't have to have an extensive twenty foot stream flowing into your pond (although if you want that, we don't blame you!!). Check out the diagram below for a simple creek set-up.

filterfall waterfall stream pond
Notice that the "stream" is a longer, shallower bed filled with river rock. 

Your stream can be as short as just a foot or two, but it will make a big difference! As water flows over the river rocks in the stream, debris (which is heavier than the water) will sink and drop into the river rock. As the muck builds up, you can clean the muck out of your creek. Unlike a pond cleaning, you can clean your stream several times a year. AND you don't need to drain your entire pond to do it!

Read more about the benefits of adding a creek here.


Rocks and Gravel in the Pond

cobblestone boulder river rock
Here are some basic rock terms. 

What exactly is biological filtration? It's beneficial bacteria going to work breaking down and eating up all the excess nutrients in your pond that can feed algae. In order for the beneficial bacterial to do their job, they need a place to live -- like all the surfaces in your pond. If you add rocks and gravel to the pond, the surface area for bacteria to colonize will increase exponentially! Check out the diagram below.

surface area diagram

What this diagram shows is how you increase your surface area. For example: let's say in your pond you have two or three flat stones in the bottom of your pond that are about as a big as a football. They have surface area, which is good. Now imagine replacing those flat stones with the same amount of river rocks (like the right side of the diagram). Look how much more surface area that rive rock provides!

For us, having rock, especially river rock, in your pond is a MUST. You are wasting your time, effort, and money on keeping your water clear if you don't have rock. Even if you can just add one or two inches of river rock to your pond bottom, do it! We've written a lot more about rock here.


Aquatic Plants

water plants hibiscus pickerel weed butterfly
Every plant in this picture is a water plant!

Plants are natural filters all the way! They eat excess nutrients that build up in the pond. Not all plants are as good eaters as others, however. Although water lilies shade the water, they're not great nutrient eaters.

For the best results, marginal plants put in areas where water flows through their roots will be the best at filtration. As well as eating nutrients, their roots will catch fine debris too. (Another reason to add a stream!)

Plants are another one of those "must haves" for pond care. Luckily they come in a very wide range of types, and they're a wonderful way to beautify your pond. Come check out our plant selection.


Supplemental Beneficial Bacteria

bioclear and clean natural bacteria cool ponds
Clear water brought to you by.... BioClear and Clean!

In our backyards, we're trying to imitate Mother Nature. She has plenty of beneficial bacterial to keep natural bodies of water in balance. In our backyard ponds, we do things to upset that balance -- too many fish, fish food, inadequate plant quantities, etc. So it's important to supplement with BioClear and Clean (beneficial bacteria) to keep that balance by its consuming the excess nutrients.


All ponds are unique and require their own filtration solution to look their best and remain healthy. There are lots of easy ways to increase your pond's filtration or you can start with the easiest and lowest possible maintenance -- the biological waterfall and skimmer. Need some advice? All of us at Cool Ponds are happy to help! You can get all the pond filtration supplies you need from our shop.


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