Montmorillonite
(Bentonite Clay)

Fishy stories, facts and myths as told at the edge of the koi pond by Chris Neaves.

The addition of montmorillonite clays to fish ponds have proven benefits. Many koi keepers used these clays with great success. Montmorillonite clays are commercially available under various brand names depending on the country of origin. UBUMBA is a South African product whilst REFRESH originates from Japan and REFINE from England.

Montmorillonite clays, depending of the chemical composition and purity, enhances water quality, replenish and enhance minerals and remove certain unwanted wastes. The uses and benefits go further than this. Montmorillonite improves the lustre and skin quality of koi as well as heightening the colour. Added to food it is claimed to aid digestion and increase the koi's ability to assimilate the vitamins and minerals required in their diet. More about this later.

Some claims are made that organic waste such as DOC will be removed from the pond. The ionic exchange capacity is increased.

There are several forms of montmorillonite available on the market. Some products are a pure montmorillonite clay. Others are a less pure form and have to be processed to remove and eliminate impurities they are mined with and some claim to have bacteria additives. Some may have additives to the clay such as extra minerals, above what is naturally found in the clay. Whilst others are a montmorillonite clay / zeolite powder formulation.

In some parts of the world montmorillonite clays were formed during the Jurassic period many millions of years ago. Others originate from later periods. Just like all minerals in the earth the quality of the deposit will vary from area to area and country to country. Whilst some are of excellent quality others are not very pure.

The idea that Montmorillonite clays could be used in the remineralisation of ponds originate in Japan. It was also discovered that feeding small quantities to koi and occasionally bathing then in it or adding regulated dosages to the pond resulted in wonderful and significant effects on their colour and lustre.

One of the confusing aspect of commercially available montmorillonite clays is the use of two names for exactly the same mineral. Montmorillonite clays are bentonite clays and bentonite clays are montmorillonite clays. All types of bentonite clays are grouped together under the Montmorillonite or Smectite group of clays. To speak of one is to speak of the other.

Montmorillonite has the chemical formula (NaCa)0.33(Al,Mg)2Si4O10(OH)2.nH20 and was named after its discovery locality, Montmorillon in France. It has a relative density (specific gravity) of 2.0 to 2.7, and a hardness of 2. It is typically white, grey, or buff in colour but may have tints of yellow, pink, or blue. Many trace elements and minerals are contained in this clay such as - Silicon Dioxide, Aluminium Sulphate, Iron Oxide, Iron compound, Sulphur Dioxide, Calcium Oxide, Magnesium Oxide, Titanium Dioxide, Potassium, Sodium, Calcium carbonate, Phosphorous allotrope.

It is formed chiefly through the alteration of volcanic ash. We know of other members of the Smectite group under another name - bentonite. Montmorillonite is the main constituent of the rock bentonite. Bentonite is composed primarily of the clay mineral montmorillonite - (hydrated aluminium silicate) that contains other elements and trace minerals. Bentonite was discovered in Wyoming, in Fort Benton shale - hence the name bentonite.

Montmorillonite/bentonite clays are mined in various parts of the world. The largest deposits and the purest form is mined in the U.S.A. in Wyoming. Other deposits are found in Italy, Cyprus and the Philippines - and a very high grade is mined in a certain part of South Africa.

Montmorillonite absorbs water readily, swelling to a gel-like mass. This property makes it useful economically. Many industries, including textiles and chemicals, use it as an absorbent to refine out impurities. Montmorillonite is also used in drilling lubricants and as a plasticizer in moulding sands used in foundries.

By treating Montmorillionite with soda ash, the meta-bentonite Sodium Bentonite, can absorb water and swell to about 20 times their dry volume. The sub-bentonites, containing calcium become Calcium Bentonite or Montmorillonite, do not swell to this extent but are still capable of absorbing from their surrounding at a phenomenal rate.

Montmorillonite can be found in low grade deposits which will contain about 30% - 40% of its base elements. Whereas a high grade or pure form will contain over 90% montmorillonite in its natural form.

Montmorillonite is used directly in the pond water each week in the recommended dosage. Some disperse more easily than others. Some have to be mixed with water before application whilst others can be sprinkled directly onto the pond surface. The pond will clear in about 6 - 10 hours, depending on the amount of organic material in the pond. Do not be worried in a new pond if the water does not clear in a day or two.

Montmorillonite can be mixed with the food and given to the koi. Here is a simple procedure for applying the clay to the food. Take the days ration of pellets and dampen them. This can be done by placing the pellets into a tumbler or a Tupperware dish. Immediately throw the water off after a few seconds. Allow the pellets to stand for a few minutes. Sprinkle montmorillonite clay lightly over the food, turning once or twice. Allow the pellets to stand for five or ten minutes. In this way the pellets will soften from the moisture and the clay will adhere to the pellet. Because the pellet is soft but has retained its shape one size pellet can be fed to all size koi.

Do not allow the pellets to stand in the water for long periods. This is the same as allowing the pellets to float on the surface of the pond for long periods. Vitamins used in all koi food s are water soluble and will leach out if the pellet is allowed to float for long periods on the pond.

The clay can be dispensed in the following manner. Take an Aromat seasoning decanter of 200g. Use or remove the contents, rinse and dry. This makes a very easy and convenient method of spreading the clay evenly over the food as the holes at the top are large enough to allow free movement of the clay but small enough to control the flow.

Should you wish to add medication to the food you can mix it in with the clay. Add it to the food and the clay adheres to the pellet. If you wish to supplement the staple food with pure spirulina this can also be done but adding the spirulina lightly onto the damp pellets and then sprinkling them with montmorillonite. Spirulina should only be fed in very small quantities over a sustained period of time for good results.

I would suggest that this particular Aromat container be boldly marked as it could be used (and has been used) by an unsuspecting partner on your salad or food!

Regards,

Chris Neaves