Laguna Koi Ponds

(949) 494-5107


Library Multi Chamber Filtration

Laguna Koi Ponds
20452 Laguna Canyon Rd.
Laguna Beach, CA. 92651 U.S.A.
Hours of Operation:
Monday-Friday 9AM-5PM Satuday 10AM-5PM
Sunday 11AM-4PM
(949) 494-5107
Pond Calculator App for Android

The Case for Multi Chamber Filtration

The Benefits of Multiple Chamber Pond Filtration.

Ben Plonski; Laguna Koi Ponds

Ponds are like people; no two are ever alike. Each one has a unique set of variables or characteristics, which set them apart from others. Creating balance in our ponds means establishing a stable filter system and a consistent maintenance program, which will run along smoothly without a lot of trouble. Creating pond stability is within the realm of preventive care. It is taking the long view on things and not just demanding instant results. It requires patience and persistence. A proper filter system will help create a basic stress free environment where the organisms involved are in harmony with one another.

Water stability is the prerequisite to balance. Stable water conditions promote good water quality. Stable pond conditions determine how long it will take for Mother Nature to reach a state of dynamic equilibrium. The microorganisms, plankton, algae and plants and fish depend on a stable water chemistry in order to function properly without constant disruption. Most organisms in the pond are quite capable of functioning outside of perfect preconceived notions. What they are not good at is change. Endless change within the water affects all organisms negatively, not just the fish. The fish depend on these multitude of organisms to condition the water. Constant change within the pond chemistry and environment creates antagonism. The good bugs are out of balance with the bad bugs. The fish are usually the ones to pay for this antagonistic environment. A proper multiple chamber filter will encourage and support water quality and stability.

What does water stability have to do with water quality?

As I mentioned, stable water conditions promote good water quality. A lot of what we call good water quality is created by the action of bacteria and micro algae decomposing the fish’s waste products. The filter system not only filters the water as it passes through, it stabilizes the entire water ecosystem within the pond. The filter is interactive with the soup of “Living Water”. The microorganisms require stability to flourish. In unstable ponds, microorganisms and fish are inhibited by chemical and physical changes. They must adjust to changes and this takes time. The organisms are not flourishing simply because all their energy is going into adapting. Thus, our fish are swimming in a soup where natural microbial balances are out of check. We can say that the biological stability is upset. With a proper system, biological stability keeps bad bugs in check. Happy balanced Living Water acts as a natural probiotic. Probiotic bacteria is nothing new. In nature it is called bio-diversity. Natural ponds have such a tremendous diversity of organisms that no one pathogenic organism can take over. It is only when we put our koi into crowded unstable conditions that they break down and the pathogens can take over. A large multiple chamber filter will encourage microbiological diversity and biological stability.

We are making the transition from sterile thinking to stable living thinking. We have seen that what we do to the water, we also do to the fish. Our goal is to achieve maximum water quality by controlling stability within the system. The bottom line is to be flexible; understand the principles; develop your experience and adjust your decisions based on daily observations. Each pond will have to achieve stability in it’s own way. Now we will discuss correct techniques and pond systems, which are conducive to stability and lead us to good Living Water Quality


Most pond filters are simply too small. Size does matter! How do you expect to achieve stability with a biofilter that requires weekly cleaning? When a biofilter is too small for the waste load of the pond you will be cleaning it too frequently. The good bacteria will be washed away too frequently.

Try these filter sizes:

A water garden filter gallons should be 2% to 5% the volume of the pond. 1% to 3% as media.

An ornamental koi/plant pond filter gallons should be 5% or greater depending on fish load. 3% as media.

A full fledged koi display pond filter gallons should be 10% to 20% the volume of the pond. 6% to 8% as media.

When you install a prefilter ahead of the biofilter you just made a quantum leap in achieving stable Living Water Quality. A good prefilter prevents solids from reaching the pump and biofilter. Now you can clean the prefilter without disturbing the biofilter bacteria. The biofilter bacteria are very slow growing and are easily lost in vigorous frequent cleaning. A good filter system would require weekly cleaning of a prefilter and cleaning the biofilter once or twice a year! This is the difference between filtration and water purification. This is a very important concept to understand. Filtration is the removal of solids from the water. Purification is the conditioning of the water by the action of bacteria, microorganisms, algae and plants. As the water flows through the biofilter it is in contact with large numbers of bacteria. These bacteria not only consume ammonia and nitrite but recycle all the other dissolved organic and inorganic wastes like phosphates and carbon based molecules and left over small solids which past through the prefilter. These bacteria grow on and in between the media, layer upon layer in a bacterial matrix that becomes a little universe all it’s own. This stable population of bugs requires good oxygen flow and stable conditions to flourish. These bugs may take 6 months to a year or more to fully establish. Frequent “disruptive cleaning” of the filter media washes away stable colonies of bacteria. Large filters will bounce back more easily than small ones. Ponds in very cold climates will rely on many aquatic plants for biofiltration since the bacteria often freeze in the winter and a biofilter is restarted every year.

Some of the bacteria in the bio-filter and gravel bottoms consume high quantities of phosphorous. In fact, given stable conditions, some of these phosphate eating bacteria can actually grow faster than algae. They are capable of digesting enough phosphate that the algae just starves. This is how a pond clears itself of green water or hair algae when the system is given time and stability. Frequent “disruptive cleaning” of the Bio-filter or gravel bottom is antagonistic to stability. This is one reason why ponds go green after a vigorous filter cleaning. Improper filtration is also the reason ponds need big U/V sterilizers. A proper filter size and design greatly reduces the need for a U/V.

Disruptive Cleaning and Disease.

Most fish ponds have a higher level of nitrogenous waste than would be found in nature. We keep too many koi and we feed very concentrated, protein rich koi pellets. This means that our filters and water tend to have a high count of proteolytic bacteria, which consumes these wastes. These proteolytic bacteria are growing in very high concentrations in the biofilter or gravel bottom. These bugs do not belong in the pond water on the fish.

When we clean a biofilter or clean a gravel bottom, we potentially release these proteolytic bacteria into the pond. These bacteria are more than happy to continue feeding on proteinaceous material, only this time it is your koi’s skin. This is one good cause of ulcer disease. Many times I have seen koi in great shape until the biofilter was cleaned. This is one reason why a proper filter design is important. A good filter design cleans easily without excessive disruption. A good design lets go of the dirt with minimal impact to the bacteria. A good design does not release toxic filter by-products or proteolytic bacteria back onto the fish.

I remember a pond, which looked very good, and the koi were healthy. However, the biofilter had not been deep cleaned for over one year. Furthermore, it had not been completely taken apart for over 5 years. This bio chamber had a good settling tank ahead of it but we still assumed it would be very dirty. Too our surprise it was not dirty at all. The interesting part was after we “cleaned” it and turned the filter back on. All the koi huddled in the opposite corner as far away from the filter as possible for over one week. Fortunately, the koi remained healthy, but this does show that we released some very uncomfortable chemicals or bacteria, which really bothered the koi. Had this filter been full of black anaerobic sludge, I cringe at the thought of what may have occurred.

The Case for Multi-Chambered Filters.

Multichamber filter systems are more stable than a “one tank does it all” approach. You can clean one of the chambers at a time and thereby not disturb the entire system. When you clean individual chambers you are less likely to flush loose waste and bad bacteria back onto the fish. Chambers toward the end of the system can literally stay clean. A 3 chamber system is more stable than a 2 chamber system. The filter systems in and of the more serious hobbyists, utilize 4 or more chambers. I have seen systems with up to 13 chambers, which were highly successful. The bacteria in these systems can grow in peace and truly stabilize. Water quality produced by multi-chambered filters is the best. The best water quality is achieved when your filter is gravity fed and the pump is at the end of the system. I have said it a thousand times, “keep the solids out of your pump”. You instantly pollute your water when the fish waste goes through the pump. This creates an endless list of potential problems including hole disease and algae problems. In my experience, the advantages of a large, gravity fed, multi-chambered non-pressurized filter put them at the top of the list of choices available today.

A well designed multichambered filter can be successful with many different types of media. Various filter media are available which are very easy to clean of dirt without dislodging much bacteria. Japanese mat in a honey comb configuration does not trap the dirt within the media. Suspended solids are removed either through settling or other prefilter tank. This keeps the dirt out of the Japanese mat and it remains aerobic. Other media choices include ribbon types, brushes and the new Kaldness KI. The new Matala filter mats are unique in that they can trap dirt but easily let go of the dirt without losing too much bacteria. The 4 various densities of Matala can be arranged sequentially so as to trap dirt in the prefilter section and function as a highly aerobic media in the biofilter section.


Establish a consistent maintenance program to promote stability and ease back pain. The design of the pond should revolve around ease of maintenance. If you set up your filter so it can be easily backwashed, you are more likely to do it religiously. What I see all too frequently is a pond, which goes from one extreme to another, too dirty, too clean, too dirty, too clean. Letting the pond turn to garbage and then completely cleaning everything will never get you to the balanced pond you were hoping for. Alas, many pond and filter designs limit us to this kind of cleaning. Get the right filter design and you will be in charge.

Water Changes and Filter Cleaning.

Proper water changes are extremely valuable in maintaining stability. Tap water is totally different from your ponds water in pH, alkalinity, temperature, salinity, dissolved oxygen; it is sterile and contains chloramines. Make small water changes frequently. 10% water changes spread out more frequently are better than big water changes done infrequently. Don’t make big water changes unless absolutely necessary. Some emergency situations may indeed demand a large dilution. Toxic chemicals like pesticides or paint would require an immediate 70% to 100% water change to save the fish. A high ammonia or nitrite level would be better controlled with 10% to 20% daily water changes and corrective filtration principles.

Crowded koi ponds or show koi displays may need 25% to 65% monthly water changes. Be careful of chloramines. Water gardens do not require large monthly water changes.

We have seen that creating a stable balanced pond is a lot more than just producing good numbers. We have learned that to take care of the fish we must take care of the Living Water.


The quality of Living water is determined by the health of the microorganisms in a dynamic equilibrium with the filter system. The stability of the pond, chemically and physically, determines the health of these microorganisms. Water stability is an end product of planning and proper filter design. Water stability takes time and patience. It requires staying within limits. Maintaining stability requires a filter system that can be cleaned without disrupting the pond.

We have seen that a proper filter system requires a good prefilter to keep the dirt from reaching the biological chambers. A proper filter should be as large as you can fit. A proper filter system should consist of multiple chambers to promote stability. Two to three chambers is good; three or more chambers is even better. Each pond will acquire it’s own unique state of balance. Be flexible. Observe your pond water conditions and your fish every day. You are aqua-culturists. You must learn to culture stable Living Water. A good multiple chamber filter system is critical in establishing this stability.