Koi Health and Supplies » Water Quality

Introduction to Water Quality

There is a lot to know about water quality in a koi pond but learning it is not difficult. Without a reasonable knowledge of how to maintain water quality you are setting yourself up to fail as a koi keeper. Take the time now to learn the basics concerning water quality and you will gain the time back later by not having to deal with sick fish.
To begin with, you need to understand the basic nitrification cycle in a pond. Fish produce nitrogen waste which, if left unchecked, will build up in a pond to a toxic level that will kill the fish. Fortunately, there is a natural process that, when functioning properly, will break down this waste to a non toxic level through the use of beneficial bacteria. That process functions as follows:

The fish produce ammonia (75%) from their gills and (25%) from their vent. Nitrosomonas bacteria, which builds up in the pond filter, breaks down the ammonia and converts it to nitrites. Nitrites, which are also toxic to fish, are then broken down into nitrates by nitrobacter bacteria which also develops in the filter. Nitrates, which are much less toxic, are then consumed by any living plants in the pond including algae. In a new pond it takes between 4 to 6 weeks for the beneficial bacteria to develop in a filter to the point to where all the toxic ammonia and nitrites are being removed as fast as they are being produced. For this bacteria to develope properly it is important for the pH level of the water to be in an exceptable range.

With this in mind, let us look at each stage of the process:

Ammonia- When the fish eat food they produce ammonia as a waste. At high levels it will burn the gills of the fish and can cause death. Even at low levels it can create serious health problems. If the gills get burned it reduces the ability for the fish to excrete ammonia through the gills thus causing the ammonia to quickly build up inside the fish. Even low levels of ammonia in a pond for an extended period will cause stress in the fish thereby lowering its ability to fight off bacterial infections and parasites. For this reason, the only acceptable ammonia level in a pond should always be 0.

What can cause a high ammonia level?

Filtration- The pond filter may be inadequate for the pond by either being too small for the fish load or just a poor design. In the case of a new pond the filter may not have had enough time for the bacteria to develop. In cold climates the filter bacteria will die back in the winter time. If you feed the fish too much food in the spring before the filter bacteria has a chance to build back up you may experience high ammonia levels. Giving the fish a food high in protein early in the spring or late in the fall can create ammonia because the filter is not up to speed. If you add too many fish to the pond at one time you can experience an ammonia spike. If you medicate the pond with formalin, potassium permanganate or a number of other medications and do not bypass the filter media during the process you can kill off some of the bacteria in the filter thus allowing an ammonia spike. Additionally, if the alkalinity (concentration of bicarbonates) in the water is low (below 50 ppm) this can greatly reduce the ability of the nitrifying bacteria to form.

How do I solve a high Ammonia level?

Water changes are the most effective way to lower ammonia levels. Perform a 25 to 50% water change. Do not forget to add dechlorinator (Sodium Thiosulfate) to the pond before adding the new water if you are on city water. Check the difference in the water temperature between the pond water and the new water. If the difference is more than 10 degrees, add the new water very slowly so not to shock the fish. Check the ph of the new water. Ammonia is much more toxic at a high ph than it is at a low ph. If the new water has a ph higher than the pond water you might want to add a slight amount of acid to the pond to lower the final pond ph after the pond is full to around 7.2. If you suspect that the oxygen level in the pond might be low, add more oxygen. Oxygen is required by the nitrosomonas bacteria to remove the ammonia. Additionally, if the fish gills were burned by the ammonia, adding more oxygen will make it easier for the fish to breathe. Do not forget to check the alkalinity in the water to make sure it is not lower than 50 ppm. Ideally, the alkalinity should be between 90 and 120 ppm. Finally, if the ammonia level is high, stop feeding the fish until the ammonia level drops. I know this is hard for some of you but you are not helping your fish by feeding them because they are using the food to make more ammonia. If the ammonia level is not solved within two weeks you need to take a serious look at what is causing it.

Ammonia Test Kit

Nitrites- When nitrites are present at any level in the pond you need to take it seriously. Nitrites can bind up the red blood cells in fish causing brown blood disease which can be fatal. One sign of high nitrites is the fish gasping at the pond surface.

What can cause a high nitrite level?

All the things mentioned above for high ammonia levels could also cause high nitrite levels. One note is that the nitrobacter bacteria which removes nitrites is much more fragile than the nitrosomonas bacteria which removes ammonia. This nitrite reducing bacteria takes twice as long to develpoe in a new filter and is the first bacteria to die off if you run a strong medication through the filter media. Also, if a filter gets plugged up or is not cleaned often enough, nitrites will build up in the pond even before the ammonia does.

How do I solve high Nitrite levels?

Again, just like ammonia, you want to perform water changes, stop feeding the fish and add oxygen if necessary.

Nitrite Test Kit

Nitrates- are the last chemical produced in the nitrification cycle. They are relatively not toxic compared to ammonia and nitrites but can kill fish at levels over 300 ppm. In most ponds they are consumed by the algae in the pond well before they kill the fish. At levels below 80 ppm nitrates are not a problem. Levels above 80 ppm should be taken seriously though because they can cause redness in the fins and cause fish to become very lethargic. High nitrate levels can also cause stress to the fish, which in turn can prevent soars from healing even whit the use of antibiotics. High levels of nitrates can also stunt the growth of fish.

What can cause high nitrate levels?

If the pond is completely void of all plants including algae there is nothing to consume the nitrates therefore allowing the nitrate level to go up. Over medicating a pond with potassium permanganate or formalin can kill the algae in the pond. Some algae control treatments will literally wipe a pond clean of algae. Very little to no sunlight on the pond may inhibit algae growth also.

How do I solve a high nitrate problem?

First perform water changes until you get the nitrate level in the acceptable range. Next, consider slowing down on feeding the fish for a while. The more food you give the fish, the more nitrates they will give you back. Then go about solving the problem long term. You could place water plants such as Hyacinth or Water Lettuce in the pond to help consume the nitrates. For those who would prefer no plants in their ponds, of which I am one, you will need to cultivate a healthy layer of green algae on the sides of the pond. If the pond, at present, has a layer of brown algae you might want to brush it from the sides to make way for the green algae. Make sure the pond bottom is clean of any debris that might prevent algae from attaching to the pond bottom. Finally, make sure the pond gets some sunlight during the day. If you cultivate a nice healthy ? inch layer of green algae on all the surfaces of your pond, your nitrate levels should be well under control.

Nitrate Test Kit

Ph is a measure of the free ions in the pond water. Ph is measured on a scale from 1, which is acidic, to 14, which is alkaline, with 7 being neutral. The proper ph for different kinds of fish can vary considerably. When it comes to koi, most people agree that a ph of 7.2 to 7.4 is ideal yet I am not sure if anyone has ever asked a koi exactly what ph he likes the best. In cases where the ph is too low (5.5)the fish can experience a condition known as Acidosis which can kill a fish in just a few days. In cases where the ph is too high (9.5) fish can experience a condition known as Alkalosis which can also be fatal. Note ? Koi do not like extreme ph changes. I have seen healthy koi living very happily in water with a ph as high as 9. What drives them crazy is when you keep adding acid to lower the ph to 7 and three days later it is back up to 9. Personally, if my pond?s ph was steady at 9 or below I would not touch it. I would be much more concerned about a ph of 6.8 because you are not far away from a ph crash.

What can cause the ph to fluctuate?

A high ph is usually caused by the surroundings such as lye leaching out of the cement in a pond or any rockwork touching the pond water. Sometimes the water used to fill the pond may have a high ph to start with. On the other hand, a low ph is usually caused by the organic life in the pond. The ph can drop, sometimes very quickly, due to the following reasons:

1) Oxygen consumption due to the natural nitrification process of the filter. When the ammonia is converted to nitrites the process consumes oxygen and gives off carbon dioxide. The carbon dioxide then forms carbonic acid which in turn lowers the ph.

2) The fish also give off carbon dioxide which also quickly converts to carbonic acid thus adding to the ph lowering.

How do I control the ph?

The key to controlling the ph is to ?buffer? the water. A buffer is anything that will bind up any free ions that are released into the water. Adding baking soda (sodium bicarbonate) is a quick fix to a ph crash. You could also add oyster shell, crushed coral, dolomite or limestone but these all react much slower and need to be placed near moving water to be effective. To check how buffered the pond is you can simply test the Alkalinity. (Note- Alkalinity can mean two different things. When the ph is over 7.0 it is called alkaline. Alkalinity can also be used to refer to the buffering capacity or the concentration of bicarbonate in the water.) The alkalinity or the concentration of bicarbonate in the water should measure between 90 and 120 ppm. At that level there is little chance the ph will crash. When the alkalinity drops down to 30 ppm your ph can begin to swing both up and down. Adding baking soda is an easy way to increase the alkalinity. To raise the alkalinity with baking soda simply follow the dose chart below. Ammont to be add is in ounces.

Example: If you had a 3000 gallon pond with an alkalinity level of 30 ppm and you wanted to raise the alkalinity up to 100 ppm, you would need to increase the level by 70 ppm. Referring to the chart above, you can see that by adding 49 oz of backing soda to the pond you would reach the desired level of 100 ppm. (note that there are 16 oz to a pound.)

Special note: If the pond alkalinity is low it can also prevent the beneficial bacteria for the biological filter from forming. When starting up a new filter always check the alkalinity. Additionally, no matter how much baking soda you add to the pond the ph will not go above 8.3. At that ph the baking soda will begin to precipitate out of solution. This is important to know because if you experience a serious ph crash and the fish are dying you don?t need to worry about measuring out the exact amount of baking soda to adjust the ph. Just throw the whole box in the pond. I promise you the fish will not be upset with you.

In conclusion, having a test kit for each of the basic four water parameters is invaluable to maintaining your pond. In just ten minutes you can tell exactly what your water quality is. As stated at the beginning, "taking the steps necessary to maintain good water quality in your pond is time well spent."

ph Test Kit Digital pH Meter

Oxygen? levels in a pond are very important to the overall health of the koi. It is important to realize that plants and algae produce oxygen during the day light hours, however, at night the whole process is reversed and plants and algae actually consume oxygen. This is important because sometimes people will turn off their pumps at night to conserve energy and wake up to a pond full of dead fish in the morning and have no idea what happened. We saw one case where a man had turned off his pump at night for two years and never had a problem and then during one hot summer night he lost them all without any? warning. The problem was that the koi had continued to grow until they reached the critical point to where the oxygen in the pond, during the night, could no longer sustain them.

The most common way to add oxygen to the pond is by use of a water fall. Anything that disrupts the pond surface will help add oxygen. The only place where oxygen can effectively be transferred into the pond water is at the pond surface where the atmospheric pressure on the water and the oxygen is equal.

Placing an air stone in the bottom of a pond will not add any oxygen into the pond until the bubbles reach the surface and break. The major advantage of using an air stone at the bottom of the pond is that as the bubbles float to the surface they bring along with them the water from the bottom of the pond which is usually low in oxygen. This creates a constant current of water moving from the bottom of the pond, where the oxygen level is low, to the surface where it can pick up oxygen. The down side of air stones is that often times they end up causing the pond to look like a Jacuzzi, making it harder to see the koi because of all the bubbles on the pond surface. An alternative to air stones, that works well, is to use jets to move the water to the surface where it can be oxygenated. The advantage of using jets to move the water, instead of air, is they cause much less disruption on the pond surface.

The only way to accurately test the oxygen level in water is to use a digital oxygen meter. Oxygen testers start at around $175.00, so for most people it is not practical to purchase one. Therefore, most people will have to guess as to how much oxygen their pond contains. As a rule, if the pond has an average sized waterfall and you can hear the water flowing you most likely have enough oxygen. On the other hand, if the koi spend most of the day near the water fall or are constantly near the surface of the pond you may need to increase the oxygen level. A pond with a consistently low level of oxygen can contribute greatly to koi fish that don?t grow or that are often times sick.