There is more than meets the eye to keeping koi—much more so than the casual observer would appreciate. Maintaining healthy water and healthy koi can be a real labor of love.

If you are not a koi owner but are considering a koi pond, here is a checklist of 21 Things You Should Know Before You Become a Koi Owner.

Even some seasoned koi kichi might not have, or even know about, all of the tools of the trade at their disposal. In some instances, they may have even put off learning new methods because they were happy with the condition of their ponds and simply thought alternatives weren’t necessary.

Here is a look at 10 things more than a few koi owners would tell you they can’t remember living without.


Koi Pond Bottom Drains

Where were we before this glorious addition to koi pond filtration efforts?! A bottom drain — so named for being…well… at the bottom of a pond — is a relatively low maintenance way of filtering out organic debris.

As larger debris and fish waste make their way to the bottom (via gravity), they are removed either through natural movement or sucked in through mechanical means, i.e. a pump. Koi keepers will beg to differ as to which is better. But this is nothing new for koi keepers!

Newer bottom drains now come with a built-in aerator attached to the top guard. With this aeration, the drain has the benefit of adding oxygen back into the water column, while also creating a current that helps to circulate debris along the bottom and into it.

Bottom drains are usually 3” or 4” in diameter. Depending on the size of your pond (how wide versus how deep) and the gallons per hour you are looking to move through your filters, there are suggestions on the number of bottom drains you should add. Again, this is something that is debatable and worth looking into (like this thread on koiphen).

Here is a helpful DIY bottom drain installation guide from the folks at Sacramento Koi detailing the steps as well as some of the reasoning for the methods.

This YouTube video from the Pond Digger explores the design and layout used for bottom drain installation.


This is the first line of defense when it comes to removing larger organic debris from the surface before it sinks. Removing floating debris (like leaves) can reduce the amount of waste the other filters will need to handle. Skimmers are especially useful in a wooded or heavily shrubbed area. They can be installed depending on need or circumstance, whether it be retrofitting, a new build, or simply dropping one into an existing pond.

There are a variety of skimmers:

  • Box Surface skimmer
  • Submerged surface skimmer
  • Floating skimmer

They come in a variety of shapes and sizes to handle flow rates as well as pond sizes.

They are a fairly easy addition to any pond. In some instances, like floating pond skimmers, they can literally be dropped into a koi pond and turned on.

Foam Fractionators

Sounds like something you’d expect to see in a lab, (and it kind of is), considering the large biology experiment that is your koi pond.

The purpose of a foam fractionator (which also goes by Phoam Phraxionator) is to remove any Dissolved Organic Compounds (or DOCs for short) that are too small for your filters to catch.

So how does it work? Like this, according to this Atlanta koi club pdf:

Foam Fractionators work on the principle that most DOC and nutrients in the water have bipolar properties, meaning that one part of the compound prefers air and the other part prefers water. This means that these compounds are attracted to the air bubbles in the water, where there is an interface between air and water. When sufficient DOC has bound to the air bubble, stable foam is created and collected. The smaller the air bubbles, the larger surface area and more effective the Protein Skimmer or Foam Fractionator works. This is the principle that turns milk bubbles into foam when a child blows air into it with a straw. The bubbles mix the air and milk proteins into a foam because proteins cling to the air bubbles. The foam rises and can be separated from the liquid.

This filter can be made fairly easily from materials you will find at your hardware store (as outlined in this How to make a phoam phraxionator, 1300-1500 gph thread).

If you see how much floating organic material this removes, you won’t believe just how much is left in your pond even after good biological filtration.


Flow Through

This is a great way to get rid of the old and bring in the new. When coupled with an auto fill, this method of water removal means no water changes need to be done, so there’s never a skipped change.

It is a constant water removal/water addition system. Water is removed via the bottom drain to a wastewater removal system (sewer line, ditch, etc.) and then newer, fresh and mineral-rich water is added through an auto fill.

As the “water change” is not as drastic, your koi are less likely to get stressed because they don’t notice changes in the water parameters. Another benefit is that no DeChlor is needed.

Auto Fill

An auto fill is a great means of automatically adding water to the pond when using a flow through system. But even without a flow through, or if you are in a climate with high evaporation, an auto fill can put a koi owner’s mind at ease, knowing that their water levels will not drop to dangerous levels.

Most auto fill systems are set to adjust to water levels as they drop and will switch on automatically when water levels dip. More hands-free pond maintenance!

Sump Pump Float Switch

illustration of a sump pump float switch for koi pondIf you are worried about going to sleep one night and waking up to an empty pond, this will help you get a good night’s sleep.

It is a fairly simple solution to avoid having all of your water pumped out of your pond. The float is plugged into an available GFI outlet and then your pump is plugged into the switch (usually on a piggyback plug).

The length of the cord attached to the float is then set to a maximum and minimum water level (see diagram). If the pumps start to drain the pond for any reason, once the float hits the preset minimum water level, the pump will shut off. You may wake up to lower water levels than you like, but your koi will be ok. Stressed probably, but ok.


Drop Test Kit

As many koi owners find out at some point in their koi keeping experience, clear water is not always good water. Get yourself a drop test kit and remove any doubt.

A simple internet check will offer a pretty big selection of brands and types of testing kits — at vastly different prices. Ensure whichever kit you decide to use tests for wide range pH, Ammonia, Nitrite, Nitrate and kH API with which to test your water. A conscientious koi keeper will spend a lot of time monitoring water parameters so a good kit can be extremely useful in saving headaches and heartaches down the road.

Pond Netting

Nets have a two-fold function. They keep what is outside the pond out, and what is in it, in.

Koi are jumpers. A new koi or a stressed koi is likely to jump. More than a few koi kichi have come outside to see one of their koi lifeless on the side of the pond.

If you live in a wooded area or rely on trees for shade, a net keeps all those falling leaves and sticks out of your pond, resulting is less clean up and less decomposing organics at the bottom of your pond.

It can also be useful in keeping winged (and legged) predators out and koi in if there is enough flooding that water levels rise above the top of the pond.

Koi Net

Sometimes coercing a koi out of the pond by hand is not an option or takes too long in a pinch. Even if it is just to check on your koi or to move them to a new location, getting them out of the water is a must. Enter nets.

There are plenty of nets on the market, but to ensure the safety and health of your koi, getting the right type of netting is important.

Most cheap nets are made from coarse, knotted material with large holes, which will hook on the koi’s fins. The only way to untangle them is to cut the net or break their fin.

There are three general types of net for handling your koi:

  • Pan net
  • Dip net
  • Sock net

Each option comes in a variety of sizes and shapes. These nets are made from a soft, woven nylon fabric with small gaps so that no part of the koi is not contained.

For a little more information on the nets and tips to use them check out our Inspecting Koi Fish: To Have and to Hold article.

Also, here’s one of our videos on how to net and inspect your koi:


Broad Spectrum Disease Treatment (BSDT)

No matter how clean you keep your water, parasitic and fungal infections can happen. Something as simple as bird poop or an amphibian visitor can introduce diseases into your pond. And once they are in, they can be tough to eradicate.

The most common broad-spectrum disease control product is EcoLab’s Microbe Lift. It is a proprietary mix of Formalin (a solution of formaldehyde) and water and Malachite Green—both proven effective against topical parasites like Ichthyophthirius (Ich), Costia, Trichodina, Chilodonella. It is also helpful in treatment against Oodinium and fungal infections.

Make no bones about it, Microbe Lift is a poison, so it needs to be administered correctly and followed with the requisite water changes.

However, when you need it, you need it, so it is best to keep on hand so you won’t have to wait for shipment. These different parasites can have different life cycles according to water temperatures — so you’ll never know when an emergency situation might arise.

Clove Oil

This is commonly used to sedate koi for treatment. It can be found behind the pharmacy counter at Walmart or at a health food store. Some koi enthusiasts will be quick to point out that clove oil is used to euthanize sick koi. However, the dosage used and time administered is vastly different.

Clove oil used at 7 drops per gallon for 3-5 minutes is not going to kill your koi. Once the koi is safely back in the pond it will shake off the effects of the clove oil and be back to normal in no time.


A package of tricide-neo used in treating Koi fishIf your koi has a superficial infection or lesion, Tricide-Neo is the go-to solution. Although it is an effective stand-alone treatment against bacteria, it is highly effective when used in conjunction with antibiotics.

It operates by degrading the bacterial cell wall, causing osmotic collapse, and severely reduces the efflux pump’s effectiveness. The holes also allow easier access to the antibiotics, speeding up their effect.

So in short, have some on hand—especially in spring when bacterial infections are more likely as the koi’s immune system gets back up to speed during Aeromonas Alley.

Of course, there are probably many other techniques or features that koi owners have discovered and perfected down the years. We think these are probably the most important 10, however, and we would love to hear about yours!

1 response

  1. Fernando Urrutia :

    The float switch it’s almost never mentioned on blogs and diy sites dedicated to koi ponds… And when it’s mentioned it’s always put on the “extra parts” for the design and construction giving priority to drains and filters (mechanical and biological) and while not one can deny the importance of understanding and proper construction of the filtration on koi ponds as the foundation of healthy project, the float switch it’s a guardian angel that can make the difference between a pond that will need 100 gallon refill vs four of five 12″ kio dead at the bottom of the dry pond liner!

    I installed my switch maybe two months after my fishes arrived and on the very first week after the installation the return pipe got clogged with some filtering mat and it overflow overnight, thanks to the switch the pump was off and the koi were swimming like nothing was going on.

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