Koi Pond

There is simply nothing better to have in your garden that a koi pond.

Sitting by the pond in my backyard with a cuppa watching these magnificent fish swim around in the water is by far my favorite past-time.

If I’m not sitting fish watching, I’m tinkering with the pond.

And I love it.

Ponds come in many shapes and sizes but today we are going to talk about Koi Ponds and the lessons we have learned over the years constructing and maintaining them to save you from potential mistakes and hopefully save some money along the way.

Many years ago I used to keep goldfish in a pond but now I am hooked on koi fish

First up, a koi pond is not a normal pond, not as easy as chucking a liner into a hole and filling it with water, nor is it a cheap hobby.

What is a Koi Pond?

If I was to explain this in a few sentences it would be this:

“A koi pond is a purposed built pond designed to house Koi Carp with sufficient filtration to maintain a health eco-system so they survive and thrive.”

green pond water
koi pond
designing a koi pond

Koi Pond Design

Design is my favorite part of the whole pond building process. I’ve seen some wonderful water gardens, water features, pondless waterfalls, fountains, and even a converted swimming pool. but the majority of these were no good for housing koi fish.

I’ve also seen some horrors…

Let me explain.

Koi fish need plenty of space to swim about – especially if you want them to grow to a decent size. The pond itself needs to be very well balanced to keep up the water quality so they don’t get sick.

It will need to be about 3 feet deep if possible, but I have seen plenty of shallower ponds full of koi and they do just fine. Koi will live in a normal fish pond but outgrow them over time and you either have to build a bigger pond or give them to somebody with the space to keep them.

You need to think about koi pond construction. This is not a fish tank that you can just plonk into the ground. The koi pond can be made from concrete blocks and fiberglass or a rubber butyl liner. Both of these methods are very different and both can produce the perfect pond for your koi.

Koi fish need plenty of room so do your maths at the very start of the project and work out a cost for construction.

Koi produce a lot of fish waste – far more than goldfish or other small pond fish. They require a lot of maintenance to keep them happy, and this all starts with your pond.

Koi waste needs to be broken down rapidly to avoid producing nitrates in the water that will cause them harm. Good filtration, either by a bog filter or man-made filter is a must. Plants are also a great addition to any pond so plan for them too. You may need to add a plant shelf or two. Add one step in at least because it gives you somewhere to place smaller plants which give the koi somewhere to hide and spawn.

Think about lighting – are you thinking about underwater lights for the pond? If so then you need to consider running electrical cables int your pond which is a challenge in itself.

Laying out your pond.

Don’t make the mistake of putting your pond way down the back of the yard because once established and stocked with fish you are going to be spending a lot of time there. Try to position the pond as near to a window in your home or patio area as possible so you can sit and enjoy pond watching while having a nice cuppa. Add some lighting and you can spend a nice evening with friends on the patio relaxing and enjoying the pond too.

A great tip you can use is to take a length of hosepipe and lay it out on the ground roughly where you want the pond to go. You can tweak the design over and over until it suits your space without ever having the spade hit the dirt.

Try aim for fairly level ground and make sure you have enough room for your filter pit and have easy access for pond maintenance. If you are planning a bog filter – even at a later date, plan for it now and leave enough room to build it later.

The pond has to suit your garden, but your garden also has to suit the pond. Large overhanging trees that shed leaves and other debris in the Autumn can be a pain but if you have a skimmer installed in your pond this will take care of it – or you can put a net over the pond to catch the majority of the leaves during fall.

All these leaves, if left in the pond will sink to the bottom and turn into nasty sludge over time which causes harm to your fish so its best plan for them now and avoid if possible.

Now is also the time to think about the landscape. What features of the garden can you incorporate into the layout. If there is a hill or mound then you could consider adding a waterfall and aquatic plants in a stream or water garden section.

A pond can transform your backyard if planned properly so take your time and see if its right for you.

Koi are quite fussy fish and don’t like poor quality water. A new pond looks great but will soon turn bad and harm all your fish if you don’t have the right setup.

That leads us on to filtration

Koi Pond Filtration

You need to consider pond filtration right from the start. Water quality is the single most important factor in Koi keeping and with the right filter setup – either man-made or natural – your koi pond will be ok.

We could talk all day about filtration but here are the main points and filter types to consider:

Man-made DIY koi pond filter

These types of filters can be bought straight from the shop and just plumbed in or like me you can design your own and built it to suit your pond. Normally I will have 3 stages to the filter:

1. Settling Chamber – This is normally fed by gravity from a bottom drain and its primary function is to remove the larger solids from the water. The water enters the chamber via a 4″ pipe and swirls around causing the solids to drop to the bottom and the ‘cleaner’ pond water to drain through outlet pipes higher up in the box.

2. Next up is the static bed section of the filter. This is where some of the smaller particles and waste are filtered out of the water. I like to use something like K1 or OASE filter media in this section because it does a fantastic job of removing the muck and is a great breeding ground for beneficial bacteria.

3. Last but not least is my moving bed. This also contains K1 media, but this time I have a couple of airstones pumping oxygen into the filter to help the bacteria grow. It also helps oxygenate the water which is essential for a healthy koi pond.

The water is pumped from the last stage of the filter back through a UV light and then to the pond via a couple of pond returns that help circulate the water.

This setup has allowed me to hide most of the filtration with landscaping and because I use a bottom drain and skimmer there are no pipes hanging into the ponds water or around the yard.

Here are the full details on My DIY pond Filter that I built from scratch. I have gin-clear water because of it.

Bog Filter for your Koi Pond

Next up I want to touch on bog filters for ponds. These are a bit of work to set up but well work the time in the long run and help you achieve crystal clear water once established.

A bog filter setup requires a section off to the side of your pond full of gravel for planting. You pump the water via a series of vented pipes under the gravel and the plants, once established, remove all the nutrients from the water and it returns via a waterfall or similar back to the pond.

There are literally hundreds of designs online for bog filters but this is one of my favorites.

A bog filter is like its own ecosystem and this water garden will produce beautiful clean pond water and provide plenty of room for bacteria to grow. Plant it out with some small plants and watch them flourish. We often see these positioned at the back of waterfalls, adding an extra dimension to the pond. You can control the flow into your bog via a pump or valve in the piping so as not to overload it.

A great way to incorporate a bog filter is to build it like a pondless waterfall and then pump the water back to your pond.

They also reduce overall maintenance for your garden pond because they filter out most of the muck from the water

Buy a filter

If you are not that good with your hands or don’t have the room for a bog filter then you will need to look at purchasing a filter for your koi ponds.

Again there are many options but if you are looking for something compact that will get the job done then a decent pressure filter would be a good choice, and they don’t cost too much either.

Look for one that has an easy to clean system and a UV clarifier built-in for the best bang for your buck.

What else do you need?

We briefly mention bottom drains and skimmers earlier but I would allow for these if possible right from the start.

The bottom drain takes care of all the muck in the base of the pond and the skimmer looks after all the leaves and debris that fall on the surface of your pond water. Pond maintenance takes time but with the right setup, you will reduce this so you can spend more time enjoying fish keeping.

Your pond will never be perfect but that the joy of it all. Try and make it as natural-looking as possible.

We get a lot of questions all the time and here are some of the most popular:

Are koi ponds high maintenance?

They can be if you don’t plan them out from the start. A koi pond is not a normal garden pond, nor is it just a water feature. You will need pond pumps, filtration, a good understanding of water quality, plenty of food, and a way to remove all the waste in a safe way. As mentioned previously, koi fish are particularly fussy fish and need to be looked after.

Add a bottom drain, a skimmer, and maybe a fountain or air bubbles to oxygenate the pond and you are off to a great start.

The first thing you see when you look at your pond is the surface. Keep this clean via a skimmer or net. Floating debris looks bad but is also bad for the health of your koi.

Are koi ponds expensive to maintain?

If you don’t plan things out from the start they can get very expensive very quickly. Take the time to plan out your layout, filtration, landscaping, and research the products you need to build this outdoor pond and your fish and your wallet will thank you for a long time. Pond supplies are expensive so make sure you only have to buy them once. The right kit at the start of a project may cost a bit more but it will work out cheaper in the long run.