Water Quality

Introduction to Water Quality and Koi Fish Care.

Having a Koi fish pond is a fantastic and great experience. It’s been known to reduce stress, anxiety and is an extremely enjoyable hobby. It will bring beauty to your yard for you, your loved ones and friends to enjoy. However it is a living and breathing entity so it does require some effort to keep it at its best.

We will talk about some helpful Koi fish care tips to keep it looking amazing and healthy!

Water Quality

Koi fish care and water quality is most important for your Koi fish pond. If you have bad water quality your Koi fish will suffer from it quickly. It can reduce red, white, black and other colors in your Koi fish. Lead to parasite outbreak quicker and can kill. Be sure to check your Koi fish pond water quality and adjust for any changing conditions that you might have!

Many people ask, what is the best way to have good water quality? There are many factors.

  • Testing Water Quality
  • Good Bacteria
  • Feeding
  • Filtration
  • Oxygen Levels
  • Over Stocking
  • Temperature
  • Water Source

Testing Water Quality

Test your water quality regularly to make sure that your water conditions are in the proper range.

Test Kits can be purchased at most places that sell fish

  • PH – 7.0 to 8.3 is an acceptable range
  • Ammonia – 0.00
  • Nitrite – 0.00
  • Nitrate – 0.00
  • KH – 80 to 200 PPM is an ideal range

Good Bacteria

Good bacteria colonies needs to be in your pond to eat fish waste that the mechanical filtration system would never catch. Even with a crystal clear pond if you did not have good bacteria in your system, fish would suffer from high ammonia and nitrite levels leading to many health issues. You can let your pond achieve it naturally in which can take up to a year but most people use bacterial additives that speed up the process dramatically.


Over feeding can be a good way to make your fish larger quicker but it can also lead to horrible water quality. You need to have the proper filtration to counter act how much waste your Koi are putting out in your pond. I know it is almost impossible to not want to feed them constantly but too much food can lead to unhealthy water quality that will lead to unhealthy Koi. So try to keep it on schedule with the proper time of the year and temperature.


Filtration is going to be one your biggest concerns. Having the proper koi pond filter for the size of your pond and amount of Koi and other living animals you have in it is key to having good water quality. A good mechanical and biological filter working together is one of the best ways to ensure that your water quality is in the proper parameters. Most everyone will agree that there really is no such thing as to much filtration. The more the better! Having a mechanical and biological filter that is rated for well over the amount of water and Koi you have in your pond is in my opinion the best and easiest way to have great water quality and healthy fish.

    Mechanical Filtration

  • Is the koi pond filter that will be cleaned by you most often. This stage of filtration is what catches fish poop and organic waste that you can see and will need to be cleaned on a regular basis. The bigger the better and less you will have to clean it. You can build your own or buy one. There are so many types of mechanical filters out there on the market “cheap and expensive” so do your research on what would be appropriate for your pond and how often you want or have to clean it.
  • Biological Filtration

  • Is the Koi pond filter that will be cleaned least or if ever. This is the filter that will house the good bacteria that eats the Koi waste and organic waste that you cannot see and is a must in pond keeping. Every time you clean your mechanical filter which is going to catch the large waste you can see, you wash away good bacteria that is going to need time to bounce back. Your biological filter is the key to having those good bacteria colonies that do not get washed away when cleaning your mechanical filter. Just as mechanical filters you can make your own or buy one retail. They can also be cheap to very expensive so like I said before do so research on what is best for the size of your Koi fish pond.

Oxygen Levels

Another must and more is better! Everything in your pond breaths oxygen, the Koi, good bacteria, plants and anything else you put into it. If your koi are near the surface or by a waterfall gasping for oxygen then you most likely do not have enough dissolved oxygen in the water. Dissolved oxygen is microscopic gaseous bubble that mix with water that aquatic life uses to breath. Important right? So the best way to get oxygen in the water is with an oxygen transfer. Bubblers and blowers do this by rising water from the bottom of the pond and allowing it to come in contact with air. Most people believe that it is the “bubbles” from aerators and blowers themselves that do this, in which is true but MOST of the dissolved oxygen comes from when water hits the surface of air and that is when oxygen is most absorbed. So having a good aerator or water pump that can push more water to the surface of your pond is going to put the most amount of dissolved oxygen into your water making EVERYTHING healthier.

Over Stocking

The more Koi you have in an area of water the more waste the filter has to process. If your filter cannot process the amount of waste then the water quality of your pond is subject to decrease. You can counter act over stocking of Koi with having a larger filtration and aeration systems in your pond. Be careful though if you want your Koi to grow Huge “up to 40 inches” try not to over stock because fish naturally release GHI “Growth Hormone Inhibitors”. What is that? GHI is a hormone fish release naturally into water saying I take up this many gallons of space to grow larger! If you have too many Koi in a pond releasing too much GHI into the water then you can stunt their growth not allowing them to reach their potential full size. So if you want to have large Koi plan out how many Koi you can put into your pond at the size you want them to be at as an adult.


Temperature is also important in Koi fish care. More northern states don’t have as big of an issue with hot weather as southern states because Koi do enjoy cool to cold water.

    Hot Temperatures

  • If your Koi pond has 12 hours of direct sunlight it’s going to heat up. Try to give your Koi pond a blend of sun and shade so that the water stays more at an acceptable range. Great aeration can help to lower your ponds temperature and is a must if your pond tends to get hotter in the summer because hot water does not hold as much dissolved oxygen as cold water. You can add shade canopies to your pond if there is not an acceptable area in your yard with shade.
  • Cold Temperatures

  • For winter season you can also add more aeration to your pond so it does not completely freeze over. Remember if your pond completely freezes over it will not allow an oxygen transfer and your koi will not be able to breath. If you live in an area that no matter what you do and top of your pond will freeze over your best bet is to house them inside a warmer area in a quarantine tank for the winter months or heat your pond with a pond heater “can be very expensive to use a pond heater”.
  • We do not feed our Koi if the water temperature or quarantine tank is under 50 degrees Fahrenheit. They might not be able to process the food in their stomach and it can make them sick or even die in extreme cases. So even if they are begging for food and the water is to cold stand your ground. A good suggestion is to try to bulk them up over the summer so they have more than enough fat on them in the winter months to not have to eat.

Water Source

    Well Water

  • The best water source for your Koi fish pond is from a dug well or natural spring. Natural spring water is water that flows to the surface from a clean underground water source. It is considered to be free of most contaminants typically found in city drinking water. It also contains a level of minerals that is beneficial to health for most living things. It is typically neutral on the pH scale so you will have to raise or adjust your ponds pH when you do a water change in your Koi fish pond. One thing that we do to counter act low pH is we have whole or crushed oyster shells in our Biological filters. Why you ask? Well as oyster shells break down in water they release pH and KH into the water keeping the pH in our ponds at a very acceptable 7.6 to 8.2 range. In the last couple years of using oyster shells in our ponds we have not had a pH crash one time. An even greater benefit to it maintaining our pH is that it also act as Bio Media for our Biological filters.
  • City Water

  • City water is not the best source for your Koi fish but it is acceptable. Yes it does have chemicals in it to make it safe for us to drink but those chemicals can be harmful to aquatic life. Now saying that there are many products on the market that remove those harmful chemicals very quickly and easily from your Koi pond when you go to add more water into it.
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