Filtration Basics:

The circle of life may come to mind when reviewing a picture of the nitrification cycle. Yet it is key to mother natures design of biologically filtering waste from water. However, several other mechanics should take place in your pond if we are expected to achieve an environment in which we can expect to keep healthy aquatic life successfully. Filtering the ponds various forms of debris and waste products takes several steps and can be done so many different ways. The better we incorporate the basic features, the more likely we are to have success.

When filtering waste from a pond, it is better to Mechanically filter it before continuing onto the Bio-Filtration. This permits the Bio-filter stage to perform optimally.

The mechanical The purpose of this stage is to trap as much of the crud as possible. Such as leaves, sticks and any other items like fish waste that have settled to the bottom. Also to trap debris floating in or on top of the water.

Examples of mechanical filters:
Skimmer, screens in front of intakes, filtering media, brushes, pump baskets and settling tanks to name a few. Surface debris is removed using skimmers. Since crud settles, using a bottom drain as a source for intake permits this crud to be removed from the pond to some type of separation chamber. Screens or baskets in front of pumps are important in keeping pumps from clogging. They also prevent damage to the pumps impellers.

Responsible for biologically converting organic wastes from animals and plants to water, new cells and gases. Bacteria thrive in a ph range from 6.5 to 8.5 and will not survive at a ph of less than 4.3 or above 10.5. Since fish release ammonia, then this toxic chemical requires some sort of bio-filtration to convert it to a final product which is not toxic.

There are both Pathogenic (Bad Bacteria) and Non pathogenic (Good Bacteria)
Aerobic (require oxygen) and Anaerobic (absence of oxygen) bacteria.
Since pathogenic (generally anaerobic) bacteria cause disease, it is preferable to introduce and promote growth of a larger number of non pathogenic aerobic bacteria.

The bio-filters need to provide adequate media surfaces for bacteria to flourish when environmental demands increase. Over stocking a pond is a common mistake made by pond keepers that ends with fish mortality. Most lakes have a smaller ratio of fish to water volume then the ponds most of us create in our own yards. Since the good bacteria attach to and grow on the media, flowing water helps wash away decaying bacteria and bring fresh chemicals. The more media surface, the more good bacteria the filter can support. Bacteria is abundant throughout the pond in the water and on all pond surfaces. Increasing the oxygen levels also benefits the ability for bacteria to flourish.

Chemical filtering Since the Nitrification cycle is a filtering process, it should be understood well if you plan on keeping fish. Other chemical filtering requires addition of commercial products to routinely break down biologically and degrade most forms of waste present in typical Koi ponds. This method breaks down not only fish waste, it breaks down leafs and other debris that have fallen into the pond. It can remove pesticides, odors, organic waste, excess nutrients and other harmful chemicals from your pond.

The Nitrification Cycle:

Nitrification Cycle of Koi PondFish release Ammonia; The Nitrosomonas bacteria consume the Ammonia and release a chemical called Nitrite. The Nitrobacter bacteria consume the Nitrite and release a chemical called Nitrate. Nitrates are not harmful to fish till very high levels. Nitrates are consumed by Algae and plants.

Two Good Bacteria:
Nitrosomonas bacteria
Nitrobacter bacteria

Types of Filters (Some)

Trickle towers:
These have been found to be the most optimal bio-filter design of filtering since there design adds the additional important element needed, oxygen. The water splashes over the media adding oxygen and cleansing decaying bacteria. Since the trickle tower design tends to be high or tower like in design, many look for lower profile bio-filtration type designs. Trickle towers are used by some successful Japanese Koi farms in Japan. For smaller ponds, Quarantine tanks or other small applications, consider the Tetra Filter - Read More.

Bead filters:
Bead filters have proven to be ideal in being able to keep a low profile and achieve many benefits to the beginning, average or experienced Koi Keeper. Bead filters are capable of sizing to the demand required and be done with the least amount of ease and maintenance. The GCTek Alphabead filter really is very simple to use and requires very little cleaning when compared to other filter systems. Consider the AlphaBead Filter - Read More.

Barrel Media filters:
These have long been a favorite for pond keepers since they are the easiest to design and are great if you enjoy doing it yourself (DYI). They are capable of housing plenty of bacteria and can be designed so many ways for so many different needs to fit the end users needs or requirements. Matting material is probably the most popular media used to date and can be cut to fit any design. While many other new forms of media continue to reach the market place, they all have there advantages and disadvantages and this may require some research to make any final decisions when building such a filter. Anything from plastic tubs to 55 gallon drums are used. The disadvantage to barrel filters is messy cleaning process. Matting is available by clicking here.

Underwater Gravel filters:
These filters are popular among some Koi Pond keepers. Simulating that design of aquariums that pass water down through a gravel layer. The water then returns up via plumbing. To build the lower return system, many use a network of PVC tubing that has many "T"s or PVC branch lines which are slotted to permit water to enter and not the gravel. This framework is laid out along the bottom and 4 to 6 inches of gravel is poured over. The gravel acts as the mechanical and bio filter because crud is trapped and the Bacteria grow on the gravel. The maintenance of this method requires rigorous stirring of the gravel from time to time to break up the crud lying down deep in the gravel. Different methods are used to clean this type of filter. One method of cleaning first requires users to stir up the gravel while a second tube then pulls the dirty water out and runs it through a mechanical filter to trap the crud before it returns to the pond. If the gravel is not occasionally cleaned of the trapped crud, like any filter, the crud eventually goes anaerobic and releases a toxic gas.

Sand Filter:
Another popular choice by some. The sand is capable of having more surface area for hosting good bacteria. Conventional sand filters have proven for years to give incredible water clarity. While this may be up the side, they are know for clogging problems and are capable of channeling the water. When this happens, the filter is not running in a state of efficiency and requires deeper and messier cleaning to break up the sand and crud to get the filter clean. This may have been the reason why bead filters have become so popular.

Glass Filter:
A recycled glass media is used instead of sand. This new material is 20% lighter than sand which makes it easier to clean during the backwash cycle. Additionally, because of the irregular shape of the glass media it is not prone to "channeling" like sand will. It works similarly to a conventional sand filter, which have proven for years to give incredible water clarity except, without the clogging problems associated with a sand filter.

Although the bead filters will give you exceptionally clear water, these Glass filters take it to a higher level. "This filter is designed to be placed after regular Bead Filters." Most peoples comments are "The water is so clear, the fish look like they are floating through air!"

Filter Product Page

Water Changes

Water changes are necessary. In natures design, she provides the occasional influx of rain and water shed. Some of which arrives from streams bringing with it fresh minerals. Normally, water and toxins are able to seep or penetrate the pond or lakes bottom. Our liners or cement bottoms create a barrier preventing this. To duplicate natures water changes requires draining off a percentage of water. Then make any needed adjustments in the chemistry of calcium, alkalinity and PH. Performing water changes is the final act of benefiting your ponds water quality and filtering needs. Existing pond water is teaming with life and is often referred to as living water. Rarely is it needed to drain off more then 50% of the water. The max to drain off should never be more then75%. Maintenance water changes are 5% weekly or 10% by weekly. The 5% weekly is considered less stressful for fish.

When adding water that contains ANY Chlorine, add the de-chlorinator to the pond first.

Large Pond Filtering

Building a small lake?

Filtering mechanically and biologically of large ponds or lakes 40,000 to 400,000 gallons of water is not similar to that of common smaller ponds. It just would not be cost prohibitive. Once your volume of water falls in the above parameters, then consider using nature's own engineering to maintain clarity. Enhancing circulation and aeration as much as possible can do this.

Ever notice golf course ponds. You're not likely to find a bio filtering system. Instead, you'll see quit often, some type of fountain or bubbler like fountain. The fountains they use are pulling large volumes of water up from the bottom and forcing it up and out towards the edges of the pond or lake. This large movement of water is getting aeration as it is forced up and out. Second, it is accomplishing total pond circulation. As the water moves towards the edges, it is then drawn down across the bottom to be pulled up again by the fountain. The larger the pond, the more fountains are required to achieve total circulation. For ponds that are longer, then install them centered in several locations the length of the pond. This massive amount of aeration and circulation enhances the biological bacteria to maintain a healthy pond. Stagnate water is created by the very lack of water movement and aeration.

As for the different types of fountains, consider the following model as a reasonably priced and good quality unit. Call to order.

1 Strata-Flo Floating Aeration Pump Assembly - $3,800.00 (price includes shipping)
  • 1 - 1/2 hp Strata-Flo
  • 300' cord, 6/3 wiring, 115v, Hibiscus Nozzle
The nice part about using a fountain: No backwashing like regular bio-filters...

Fountain in Pond
Perfect for golf courses, parks and retention ponds.

Strata-flo™ is the solution to your pond management headaches. The Strata-flo's™ high-flow, propeller driven output means algae, unpleasant odors, sludge, weeds and poor water clarity due to stratification are history, without the need for chemicals, dyes or labor-intensive dredging. The Strata-flo™ pumping system aerates colder, denser water from deep below in a beautiful, changeable fountain display that re-oxygenates and de-stratifies water layers, aiding in the natural biodegradation of algae for clearer, healthier, more easily managed ponds.

Strata-Flo with Hibiscus Nozzle
Spray: 3' up, 5' out

Bio Filter Bucket - A simple Do It Yourself - DIY filter
Building your own bio-filter is not too hard. For those that need a quick bio-filter, consider building this small 5 gallon filter that can use Lava Rock or most any other media. Important fact! - Lava rock if used should be replaced every year during the winter!!! Lava Rock has tiny pockets that do not get cleaned out and as the good nitrifying bacteria becomes trapped, it will become anaerobic and toxic. Don't let this keep you from using lava rock for this filter, just realize that you should throw it away after a year. This filter when completed will be above water level.

Water pump size - Recommend range 350 - 800 GPH, Max 1000 GPH.
Select an ideal pump by clicking here.

Bio Filter BucketHow to:

Take one CLEAN 5 gallon bucket, and drill 4 to 8, 1/2 inch holes close to the bottom. (1 inch or so off the bottom). Drill them all the way around if your going to set on a support in the pond. (Could set it on another inverted bucket) If you would like the water to only come out on one side because your planning on placing this filter on the ledge or side of the pond, then just drill the holes on the one side or even consider using a little larger drill bit. No drill has to be used if your safe with a sharp knife... More holes are needed if water is higher then 1.5 to 2 inches from the bottom, inside during operation. Important: Drill one more small hole close to the top in the side. This lets air in during operation.

Now place the CLEAN lava rock or other media in the bucket. Fill about 2/3 full. Snap on lid. Cut a hole in the center of the lid so that the entry water supply pipe stays snug. Water tight is not needed, just make the whole tight to help hold the water supply pipe tight in place. Then connect the water supply pipe to the pump.

If you have some media from an older filter, some of it if added inside this bucket will kick start the nitrification cycle much faster. Your new filter will be cycled in 3 to 7 days. Or, if your using older pond water, it too will help cycle the filter with good bacteria in 3 to 7 days. If you have nothing to help kick start this filter, then realize that it will take a full three weeks for the filter to cycle. Providing some ammonia is in the water. A few fish will provide this ammonia. If so, feed very little and test for ammonia everyday!

Slow way down on the feeding while waiting for the new filter to cycle. Also be testing for Ammonia. Be sure to have an Ammonia test kit on hand. If you detect higher then .05 levels, then perform a 10 to 25% water change. Be sure to treat the new water with a De-chlorinator.

This design is considered a "Trickle Tower". The benefits of a trickle tower are many. Oxygen is added as the water cascades over and through the lava rock or other media. Water passing over the media also washes away the aging nitrifying bacteria. Because of the design, larger colonies of nitrifying bacteria will be able to be present then that of a submerged bio-filter.

3 Barrel Filters - Settling, Pre-Filter and Aerated Bio-Filter

Using 55 gallon barrels work really well for making a filtration system. Keep in mind that the water level in the barrels will match that of the ponds elevation. So you may find yourself digging a large hole in the ground for the barrels unless your pond is build on a hill and the barrels are on the down hill side.

Matala rolled media works great in this design. The brushes as an option can be in the first barrel or the second. Consider trying both ways to see which provides clearer water. If you want to install a pond overflow, then the first barrel would be an ideal location by using another bulkhead and an elbow pointed up with a short section of PVC cut to the proper height. The use of aeration in the biological barrel can be considered as an option, yet having it in operation greatly improves the environment and performance of the beneficial bacteria.

Barrel Filter Diagram
Building your own barrel filter will require the following list of items. The barrels can found at your local car wash often for free to 5 or $10 each. Rinse them several times to remove soap. Connect all three bottom waste lines to a single line. The reason the bulkheads for the waste lines are not centered through the bottom is because the 55 gal. barrels typically have a ridge seam through the center of the bottom which will not permit a flat surface for the bulkheads to seal. Cement is used to shape the inside bottom.

Qty / Item (Most of which can be purchased from us) (Misc. PVC should be purchased locally)

4 2" Bulkhead
5 4" Bulkhead
3 2" Knife Valve
1 4" Knife Valve
1 Green Matala Rolled Media 22" Diameter
3 Blue Matala Rolled Media 22" Diameter
8 Brushes 4" x 18"
12 Brushes 6" x 18"
1 2" 3-Way Valve (After Barrel - Connects Skimmer and barrel before pump)
4 1" x 3" Air Stones (1/2" Threaded)
1 Hakko 40 Liter Air Pump

Important note: The flow rate through the barrels. Pump no more then 1800 gallons per hour to permit enough time for the crud to settle in the 1st barrel. (55 gal. drum - 22" dia.)

Pond Questions
360 588-0140

Pond questions help

On-Line Purchase SPECIAL
Orders over $130 can receive a $10 valued Koi Collector Pocket Guide

Not available
anywhere else!

Priceless when it comes to learning about Koi

Discount will be applied when you add the Koi Guide to your cart.

bbb rating A+