Posts Tagged ‘Koi’

Koi Ponds

Icon Written by GeoffM1968 on July 1, 2008 – 10:31 am

Ever thought of having a Koi pond in your yard but did not know where to start or if you even should put one in your yard. We will try to answer those questions plus more in this months Yard Talk. You will want to be prepared as building and maintaining a Koi pond is much different and time consuming than putting in a simple water feature. It took me about 200 hours to build our pond and then I spend about an hour every week in maintaining the pond. First things first, what minimum size pond should you have.

There are many factors which go into answering this question including how many Koi you want to have in your system. For every Koi you have, you want to make sure to have a little less than one gallon for every inch of Koi. Since most Koi will quickly grow to an average mature size of 32 inches, you will want to have a minimum of 320 gallons for one Koi. Since Koi are social animals, you will want to have at least two Koi or yours will continually try to jump out. Therefore, you are now up to a minimum pond size of 640 gallons. Lets put this into perspective so you can visualize this.

You want a minimum depth of four feet for a Koi pond. So with a pound size of 640 gallons with a depth of four feet, the dimension would then be about seven feet by four feet oval which puts the estimated volume at 658 gallons or about five average size bath tubs. Now you have an estimated size pond you need to build for two Koi. Now lets take a look at construction material and equipment you will need to maintain the pond.

The most common material to line your pond with is a rubber liner with a felt padding to protect the rubber liner from the objects in the soil from puncturing the liner. Here in Florida, I have a very sandy soil and I still used the felt padding to protect the rubber liner as it is important to start with a good foundation. You can use other and more expensive material to build your pond with the best being built like an in ground pool. You have to remember, any cement material must be coated to protect your Koi from the cement leaching its lethal chemicals and material into the pond. Once you have selected the material you are going to use to build your pond, you need to now decide on a design.

Remember from our calculations, we used an oval for our estimations for a 658 gallon pond. For a Koi pond, you do not want to have any ledges as birds, which would love to eat one of your Koi, would find this very helpful getting at your Koi. You also do not want to put any type of gravel in your Koi pond as this would let bad bacterial and sludge collect in your pond which is disastrous for the health of your Koi. Think of it like this, would you want your waste to settle to the bottom of your toilet and stay there for long periods of time? With that said, another important thing to remember in your pond design is to make sure the bottom slopes to one central location for a bottom drain to take away the sediment which will over time deposit on the bottom of your pond. I have mentioned a bottom drain so lets take a look at your plumbing and filtration system which is mandatory for any Koi pond.

Many people put in a bottom drain by putting a hole in the bottom of their pond. I propose a better way is to put in a bottom drain which sits on the bottom with plumbing going to your filter and then pump. I am only going to briefly touch on the filtration system as I could dedicate an entire article to this alone. The basics of a filtration system is to remove the particles in your pond. You can do this with a simple bead filter to a more complex chamber filtration system. You have to match the right filtration system for the pond size along with the water and light conditions. The worse your water is from the water source (municipal/well) and the more light you have hitting the surface of your pond, the better your filtration system has to be to have healthy Koi. For example, if your water source is from city water system, then you will probably need a way to remove the chlorine and the more deadly chloramines which many municipalities are using more-and-more. If you are using well water, you will want more aeration due to the fact well water has little or now oxygen which is also deadly condition for Koi. For my pond, I have two filtration systems. I have a bottom drain going to a bead filter, then external pump, and finally back to the waterfall box. The second utilizes a sediment chamber, skimmer box, bead filter, external pump, two UV Filters, and then to the waterfall box.

This brings up another part of the filtration system which drives the whole system, the pond pump. The more energy efficient and better to power your system is an external pump with a leaf basket attached. Again, the size depends on the size of your pond, the length of plumbing, and the amount of lift from the point of when the water enters the filtration system to when it exits the filtration system. The more length and the more height, the larger pump you need. A simple formula is to divide your pond volume by two to get the size of the pump in gallons per hour it needs to move. In our example, you need a minimum pump size of 329 gph.

The next important piece of equipment to help keep your pond clear is a UV Filter. This kills all small single cell organisms including bacterial and algae and is essential to both the health of your pond and keeping your pond from turning green. The size of the UV Filter is again determined by the pond volume and the light conditions. The larger the pond and more light it is subject to, the larger the size UV Filter. To calculate the minimum size UV Filter(s), you take your pond volume and times it by two to get the minimum rated gallons per hour UV Filter(s) you need. In our example, you would need a minimum UV Filter(s) capable of handling a minimum of 1316 GPH.

As you have read, there are several minimum pieces of equipment you need for a Koi pond and I briefly talked about each or mentioned what I have installed on my pond. You can add a lot more equipment to your pond depending on the size and water conditions you have. I will include several links at the end of this article you can use to do some more research if you are dealing with some special water and site conditions. With each filtration system, you will want to make sure to install several valves so you can isolate each for cleaning, repair, and replacement. I learned this the hard way.

Another important design principle for you Koi pond is to ensure the outside rim is above grade to prevent water runoff from your yard getting into your pond. Both the lawn chemicals and nutrients are not good for your Koi. Along with ensuring the outside rim is above grade, you also want to make sure any decorative rocks are above water grade to prevent your Koi from bumping into them and causing skin lesions which would be an entry point for harmful bacteria.

Even if you do not think you have a lot of wildlife, you may need to install some type of protection for your fish. For my pond in Florida, I have a lot of sea birds which inhabit my area and would love to sit on the side of my pond and pick out my Koi for a treat. To help detour this, I installed a netting over the entire pond. You could install this as a cage type system or laying on top of the pond. My pond designed enabled me to bend conduit to form around the edge of my pond. I then painted the conduit to match my rocks and strung the netting across it tying it down with zip ties. It is a bit unsightly but the alternate is not a viable option.

Now you have the basic Koi pond construction. Now lets look at water chemistry and the important variables for Koi. You will want to measure and manage the following water condition levels. Until I determined a baseline for my pond, I measure these often. Now I have determined my pond is stable so I only measure once a week or when I think something is going wrong with my pond and my Koi health. Measure the following:


  • pH – greater than 7.0

  • Ammonia – 0 ppm

  • Nitrite – 0 ppm

  • Nitrate – 0 ppm

  • Oxygen – greater than 5 mg/l

  • Salinity – 0.05% to 0.10%

  • GH (General Hardiness) – 200-400 ppm

  • KH (Carbonate Hardiness) – greater than 40 ppm

You will want to manage both GH and KH to impact pH. The most important part is to ensure you have stable pH without any pH crashes (sudden pH drop) which will kill your Koi. Again lots can be written about this so I will refer you to a couple good articles on KoiVet.com:

Lets assume you have your pond set up for at least a month and have managed all your above perimeters so that they are all stable. Then and only then would you want to introduce your Koi to the new pond. Realize, your just introduced Koi will be very jumpy the first couple weeks until they are comfortable in their new environment so you will want to watch them very closely. I ensured I had my pond covered with a net to ease my mind as I also learned this the hard way. Remember, you will want to follow a strict quarantine routine when introducing new Koi to your pond to prevent disasters results.

Daily and weekly maintenance is a must. I flush my filters weekly and do a partial 20 percent water change. I also make sure to do a visual inspection of all my Koi and pond to ensure all is going well with them. Since I utilize municipal water supply, I must also treat my pond for both chlorine and chloramine prior to adding any fresh water. You must also feed your Koi daily. Rule of thumb, feed them no more than what they can eat in five minutes, two to three times a day. I have mine set up with an automatic feeder using a Koi Cafe which is worth the price. The downside using an automatic feeder, my Koi are not as friendly as they were when I was hand feeding them as they would beg when I walked up to the pond. Now they hide from me.

I am sure many of you are now saying, is it worth all the effort and it is very important you think about that as taking one week off, could have disastrous consequences. For me it is worth all the effort.

Favorite Koi Links

Utilize the following links on better Koi Health and Pond Construction:

Koi General Health

Test Kits

Supply Companies

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