Koi clays, which are typically montmorillonite clay or bentonite clay, are utilized by many koi owners to add crucial minerals and trace elements to water that may be in short supply. In addition to being used to provide nutrients for koi, these clays are also utilized greatly in the health and beauty industry and have been for centuries, with many modern studies now backing their benefits.
With this in mind, it makes a certain amount of sense that these clays could be beneficial to koi, but do they actually work? In this article we delve into the science and studies and try to work out just how beneficial these clays actually are for our fish!
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What’s Inside Koi Clay?
Bentonite and montmorillonite clays (the two most common koi clays) are composed primarily of aluminium phyllosilicate, which are sheet-like silicates and aluminum compounds stacked atop one another in a dense arrangement (hence the large molecules that comprise clay and result in its compressed, thick nature).
In fact, most clays contain aluminium phyllosilicate – it’s actually one of the features that helps define a type of soil as clay rather than, say, loam or silt. What makes koi clays different from other clays, however, is that they are smectite clays. Smectites are poly-cationic with a large cation exchange capacity, meaning that they are able to readily absorb a large amount of negatively charged toxins while giving off useful minerals and elements. In fact, bentonite and montmorillonite clays are able to absorb as much as eight times more than any other clay, thanks to their large cation exchange capacity!
All smectite clays contain iron and magnesium, with montmorillonite also containing calcium, sodium, and aluminum, and bentonite being composed of potassium, sodium, a great deal of calcium, silica, quartz, and aluminum (both contain more chemical and mineral compounds than those listed, but these are the main ones). As bentonite is composed of montmorillonite particles, it makes sense that it would contain the same compounds as well as a couple of additional ones.
The exact amounts of these compounds depends on where the clay is found and exactly how it was formed, with the only primary difference between these two koi clays being that bentonite contains trace minerals like quartz and zeolite (similar to activated carbon).
The Benefits of Koi Clays Explained
While pond owners seem to go back and forth on whether koi clay actually works or not, this seems to depend on existing water quality, environmental factors, and where the clay was obtained from. For example, some koi clays may be marketed as such, but if not from a reputable source could just be any ordinary type of clay rather than actual bentonite and montmorillonite.
Benefit 1: Water Purification
Studies have found that koi clays are able to remove as much as 99% of pollutants from water, displaying that they are very effective at cleaning out the majority of organic pollutants. Because bentonite and montmorillonite clays are cationic, they work by adsorbing anionic (negatively charged) and neutral particles, which become essentially useless once they adhere to the clay. These can include excess nitrates, ammonia, and certain metals in your water that could be negatively impacting water quality.
Zeolites (the minerals contained in bentonite and some montmorillonite clays) in particular are able to efficiently balance pH and remove heavy metals as well as pollutants such as herbicides and pesticides. However, be aware that koi clays increase both water pH and hardness since they contain calcium carbonate. As koi are fairly hardy fish, this shouldn’t be an issue so long as their desired range of 65 to 195 ppm of calcium carbonate is not exceeded and pH does not rise above 8.
Benefit 2: Improved Koi Health
Simply placing koi clay in the pond can potentially improve your koi’s health by enhancing water quality as discussed above. Antimicrobial and antioxidant properties also help koi to heal if they have lesions or other minor injuries, as well as providing them with essential elements and minerals. For example, calcium is needed by fish for healthy bone and scale development and maintenance, as well as the osmoregulation of salts. However, fish are not able to synthesize calcium on their own, so koi clays help to provide this valuable mineral.
Koi clay can also (carefully) be added to food pellets by gently rubbing damp pellets onto the clay so as to pick up small bits of it. When ingested, the clay similarly binds organic pollutants and toxins that are in your koi’s body and enable fish to excrete them more effectively. This can result in increased growth, improved color, a healthier immune system, and greater energy. Rainbow trout that were fed a diet supplemented with bentonite clay exhibited increased growth, more efficient protein utilization, greater swimming and feeding efficiency, and decreased body fat than those fed a regular diet absent of bentonite, specifically, the zeolites contained within the bentonite.
Benefit 3: Detoxification
Organic pollutants, such as tannins, pheromones and some toxins, can bind to koi clays due to their high cationic exchange capacity, making them excellent at detoxification of water and fish. Aflatoxins, in particular, are toxins produced by fungi that are most often found in agricultural fields, and in turn wind up in waterways and ponds due to runoff from heavy rains or overwatering of crop fields.
Bodily contamination also occurs via directly consuming the crops grown in the contaminated field (some reports indicate people being hospitalized after eating corn that contained aflatoxins). They not only negatively impact water quality, but are also known to be carcinogenic in addition to reducing liver function. Multiple studies conducted have found that fish, rabbits, pigs, rats, and even humans who are given bentonite supplements are able to excrete aflatoxins as the contaminants readily bind to the clay, which reduces and in some cases eliminates the toxicity altogether. Using clay prior to exposure to toxins can also prevent adverse impacts before they even have a chance to occur. When used only in water, bentonite has been shown to reduce aflatoxins in the water by as much as 66%.
Does Koi Clay Affect Water Quality?
Depending on where bentonite and montmorillonite clays are obtained from, they typically have a pH ranging from 8.3 to 9.1 plus contain various elements and minerals, which then of course will increase both water pH and water hardness. Calcium-based bentonites have a somewhat lower pH of 7 to 8, while sodium-based bentonites have a higher pH of 9 to 10.
However, if sodium ions are present in your pond, they will bind with the clay and raise even calcium-based ones to a higher pH that consequently raises water pH. If you already have high pH (above 8) or water hardness, then you should be wary of koi clays as they may raise these numbers above those that koi can comfortably or safely live in.
In addition, any calcite present in the clay will increase alkalinity, which in turns allows for higher pH levels. If you have soft water, though, koi clays will help to provide trace minerals that are otherwise likely absent or at least in too low of quantities for your koi.
Koi Clay Dosage & Dosing Instructions
Method 1 : Mixing Koi Clay With Water
Prior to mixing any koi clay into your pond, first mix a small amount, perhaps half of a teaspoon to one teaspoon, into a small container of water and wait an hour or so. If it sticks to the container like mud rather than dispersing evenly until it’s no longer visible or settling to the bottom where it’ll gradually break down, you’ve not gotten pure koi clay and it should not be used in your pond as it won’t circulate properly and may add impurities to your water. You’ll want a koi clay that’s accurately marketed as at least 95% pure, with colloidal minerals, meaning that these minerals will easily go into suspension in the water and therefore can be readily utilized by fish, plants, and other organisms. You can see our koi clay product recommendations below!
When used directly in water, it’s recommended to use one tablespoon of clay per 1,000 gallons of water. This can be done twice a week, for no longer than four consecutive weeks. The clay can be sprinkled throughout the pond, or mixed with a bit of water to form a ball of muddy clay that will float about your pond and gradually dissolve.
Method 2: Mixing Koi Clay With Food
To incorporate koi clay into your koi’s diet, dampen koi food pellets and gently roll them in the clay. Then feed your koi as you normally would. Do not do this more than two or three times per week, again for no longer than four consecutive weeks to minimize the risk of causing gastrointestinal upset. Incorporating koi clay into their food will allow them to obtain trace minerals that they would normally get in the wild by feeding on sediment that typically doesn’t exist in man-made pond environments.
You can also simply purchase fish feeds with koi clays already added, which is beneficial as the manufacturer has already done the work to access the correct dosing per feed amount. Check here for some koi feeds with clay!
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Koi Clay Considerations & Possible Side-effects
To ensure the health of your water quality and your koi, koi clays must be used carefully and with the proper dosage. When done correctly, koi clays can be a wonderful boon to your pond ecosystem! When used incorrectly, however, your koi and other pond inhabitants can become ill.
For example, consuming too much bentonite or montmorillonite clay will still result in pulling toxins from the body and binding them to the clay, but in trials performed on humans and rats, this over-consumption slows the digestion process and causes gastrointestinal upset and potential illness as these toxins will then sit in the body longer. It is safe to assume that the same can be said of fish ingesting higher doses of koi clays than is advised.
When exposed externally, too much koi clay causes skin irritation in humans and other mammals – again, it is safe to assume that the same is true of fish if too much clay is added to the water, or is added too frequently. To prevent this, perform partial or full water changes on a weekly basis, and monitor your water quality daily in addition to, of course, following dosage recommendations closely. You must also be certain that you’re getting koi clay from a trusted source, as those that aren’t pure bentonite or montmorillonite clays could have adverse impacts.
