Most beginners in koi keeping had at one time or another kept koi in their aquariums. Some beginners have kept koi in old bathtubs, household water storage tanks and almost any water container that is large enough. Koi keeping as a hobby is steadily gaining popularity amongst people from all walks of life. Flat and condominium dwellers keep koi in tanks often made of fiberglass. Those who stay in houses with compounds keep koi in ponds often made with concrete. A fiberglass tank is a good choice to try out the hobby. Advantages include easy mobility, less costly and easy disposal in case the hobby does not turn out to be. One could learn the basics of keeping good water through various DIY filtration techniques before embarking on something bigger and more permanent like a concrete pond. Sounds advise to those who are planning on a concrete pond is to “Build it once but properly”. For those who already own a pond, be it a perfect or not-so-perfect pond, and intend on making use of it, do ensure that a good filtration system is in place even if it means you’ll have to build an extra filter. An external DIY trickle tower filter is easy to build and can supplement an existing submerged filter which is inadequate. Trickle tower filters remove nitrates efficiently. Start with cheaper, smaller koi. Have all the necessary water test kits. Read about koi keeping or better still join a koi discussion forum. I hope that any beginner to this exciting hobby will benefit in some way or another from this article. Remember that pond and filter construction, koi varieties, disease and some details from other topics are not covered here as the main purpose of this article is merely to introduce the beginner to the wonderful world of koi keeping.

Water Quality.

Importance of good water.  It is not easy to maintain good water since there are koi living in it. Koi are active and voracious eaters. They excrete waste like urine and feces into the water all the time. The waste must be removed and processed quickly in order that they do not accumulate and contaminate the water. Imagine breathing in toxic and polluted air all the time! This is exactly how koi would feel if the water were contaminated. Hence a good filter is necessary. Learn to keep good water and the koi will keep themselves well. Good water means a good filtration system. The parameters of good water suitable for koi are as follows. Temperature should be between 20-25deg C. pH between 7.0 to 8.5, KH or carbonate hardness or alkalinity measures carbonates or bicarbonates in water and should be between 4 dKH(72 ppm) and 7 dKH(125 ppm), GH or general hardness measures magnesium and calcium in water and should be between 4 dGH(72 ppm) and 10 dGH(180 ppm), Ammonia/Nitrites should register as not detectable, Nitrates not more than 40ppm, DO or dissolved oxygen of at least 5ppm. Koi generally do well in water with the above parameters. Koi are essentially cold-water fish. In countries with winter, koi hibernates in frozen ponds until the winter months are over. Deep ponds are a good way for providing koi with cooler water in tropical countries. Koi thrives in water with pH above 7. The alkalinity of water can be maintained with buffering agents like shells or sodium bicarbonate (baking soda). When the pH of water swings from just above 7 to acidic in a short time, we say that a pH crash has occurred. The drastic change in pH is too rapid for the koi to adjust to and as a result they get severely stressed. This, coupled with the reduced bacterial function in acidic water condition causes filter to malfunction and toxins to accumulate. A large number of koi are lost in this way. This usually happens in water that is low in buffering capacity. Accumulation of rotting organic matter in old ponds or tanks and low levels of carbonates reduces the buffering capacity of water. This results in a delicate balance whereby the pH will swing suddenly to acidic if it is disturbed even slightly, like after a bout of acid rain or accidental addition of any acidic substance into water. Carbonates are used up when ammonia is converted into nitrites and nitrates. Hence a continuous source of carbonate is necessary for the filter to function properly. Lime from new concrete ponds is one such source. Tap water is another. Shells kept in filter chambers are another good source of carbonates. A quick way to increase the carbonate level in water would be adding baking soda or sodium bicarbonate. 100g of baking soda would increase the carbonate hardness or KH of 1 ton of water by approximately 5-6dKH or 100ppm. A KH of at least 4 dKH or 70ppm is considered safe to prevent pH swing. Therefore hard water is more suitable to koi than soft water. However water that is too hard will also pose certain problems to koi. Ammonia from koi waste is very toxic to koi and is continuously produced and removed by the good bacteria in the filter. It is converted into the less toxic nitrite and then into the non-toxic nitrate by these good bugs. The presence of nitrate in water is a sign that the filter is maturing. Nitrate level fluctuates in a pond with vegetations. In the early mornings it may be high but slowly drops in the evenings. This is due to it's consumption by the vegetations in the daylight hours and it's accumulation during the night hours. However very high level of nitrate (more than 200ppm) in water is bad for the koi and pond even though koi can tolerate quite high levels of nitrate. A nitrate level that is too high will affect the conversion of nitrite to nitrate. This will lead to higher nitrite levels. Algae also absorbs nitrate. So do regular water changes. Trickle tower systems are known to decrease level of nitrate in water.

Green water. This is a condition whereby the water appears green and cloudy and one could barely see the koi. Green microscopic algae blooms due to favorable conditions like high nitrate level in water, exposure to sunlight and inadequate filtering capacity. However many a times we hear of green water in new ponds. The nitrate level in a new pond is definitely not high. Many new ponds with partial or total shading do experience green water too. So it seems that this phenomenon does not only exist in ponds with high nitrates and exposure to sunlight but also in new ponds where the filtration systems are not yet established. The following excerpt from Pond Water Chemistry Booklet by Norm Meck attempts to explain this. "Some of the statements that follow are somewhat controversial, but they are based on several years of research and experimentation dealing with the subject. From this research, I have concluded that within our biologic converters, a third group of bacteria exist. When these heterotrophic bacteria consume dead algae in an aerobic environment, they release an enzyme, possibly used to help them digest the dead algae. The flow of water through the media carries surplus amounts of this enzyme back into the pond where it kills off the other algae. This enzyme appears to be effective against many species of string algae as well as the bloom algae. It does not seem to have as much effect on the string algae, which is only partially submerged, or within a high flow area, i.e. in a splashing brook or around a waterfall. This may have to do with contact time requirements. The short blackish-green mat algae found on the walls of a "healthy" pond is composed primarily of dead string algae which is also believed to be a result of control by the antibiotic. Further, this mat area may also be providing a portion of the enzyme as it is being broken down by the heterotrophic bacteria." And this is the solution that he proposes. "It seems to be simply a properly sized biologic converter and a proper flow rate of oxygenated water through it. The bio-converter must be large enough to support the heterotrophic bacteria colonies which need considerably more space than just the nitrification bacterial colonies. This has led to two rules of thumb. The first is that the amount of water in the pond and filter system should be circulated through the bio-converter at least once per hour. Second is that a flow rate of approximately 150 gallons per hour per square foot of media should be used. As an example of a 1500 gallon pond, we should be moving 1500 gallons of water through the bio-converter each hour and the bio-converter cross sectional area exposed to water flow should be 10 square feet. The thickness of the media is determined by the media selection."

Filtration.

There are two types of filtration systems, 1)Gravity-fed, 2)Pump-fed. Solid waste are mechanically filtered whereas liquid waste are biologically filtered. Hence any effective filtration system should have both. Filtered water should not only be clear and free from suspended solid waste, it should also be free from ammonia, nitrites and nitrates. Another factor affecting the effectiveness of any filtration system is the size of the filter. There should be enough space for mechanical as well as biological filtration. Most also have space for vegetation to perform chemical filtration or the removal of nitrates. It has been estimated that the surface area of a filter should be at least 30% that of the pond. The bigger the better. Filtered water returns to the pond via a waterfall or venturi.

Gravity-fed filtration systems. Water in the pond enters the filter by gravity via the bottom drain and/or the middle feed (an inlet pipe in the wall at a height about the mid-level of the pond). The water carries with it solid wastes that are intact or unbroken. Once inside the settlement chamber, the heavier solids settle and water carries the rest passing through mechanical barriers like brushes and nets. Most solid wastes are stuck in the barriers while some will slowly settle down at the bottom and accumulate. Very minimal finer solids would escape into the biological chamber containing bio-media like bio-balls or Japanese mats. The bio-media becomes relatively free from debris. This results in water that is substantially free of suspended solids.

Pump-fed filtration systems. Here, water is pushed into the filter by a pump in the pond. Solid wastes sucked into the pump are inevitably broken down into smaller and finer solids by the impeller. The resulting mixture of water and fine solids enters the filter. Much of these solids do not settle but instead passes thru the mechanical barrier with only a small portion of it being trapped as they are finer. Most escape into the bio-media and gets trapped there. The Japanese mats get clogged up easily. The resulting water may carry some very fine suspended solids. There are pump-fed systems that are pressurized. They contain beads or sand that have both mechanical and biological functions. The water that comes out is crystal clear. However the media becomes clogged with debris easily or clumped together after sometime. Back flushing of the media regularly is necessary to prevent this.

Conclusion. It can be seen that for the purpose of keeping a fish like the koi, the most suitable filtration system would have to be the gravity-fed type with bottom drains. Even though this system takes up more land than the others, the benefits and advantages of having one is too important to ignore. In summary, they are, 1)early removal of waste from system to minimize contamination, 2)efficient wastes disposal by flushing, 3)effective mechanical filtration with cleaner bio-media and less maintenance, 4)cleaner pond bottom.

Biological filtration. The bio-balls or green Japanese matting support colonies of good bacteria. These good bugs convert the liquid waste ammonia into nitrites which are in turn converted into the less toxic nitrates. The good bacteria requires a lot of oxygen to survive. Hence good aeration of the biological media is important. The water that is free from toxins like ammonia and nitrites now gets pumped into the pond.