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The Mini Koi Pond 









You’ve done some research and you're thinking about becoming a koi keeper.

You would like a taste of what the hobby has to offer. 

You want a chance to learn and practice your skills before committing to building a large koi pond. 

You want something easy to 'wrap up' if you decide koi keeping is not for you. 

So, what do you do?


I would recommend building a ‘Mini Koi Pond.’ 


This doesn't mean a garden pond or a water feature, it means a perfectly designed koi pond - just on a smaller scale.


I advise you skip the stage of building an unsuitable larger 'garden pond' in favour of something small but perfectly formed. Why? Because downsizing makes it affordable to do properly and a 'Mini Koi Pond' that is easy to maintain, houses good water and can give your koi conditions to thrive, will keep you enjoying and learning about this fantastic hobby until you are ready to build a larger system. But who know's, you might find your mini koi pond suits you just fine!


Where to start?

Obviously there are many ways to construct a koi pond but for a beginner in todays market, I would consider a ready made, free standing tank. Various companies make them in many shapes and sizes from fibreglass or you can get cheaper circular versions made of plastic. The benefit of using such tanks is that there's no need for excavation, which speeds up the build, if left above ground they are safer for children and they can also be removed easily if you decide to relocate or give up the hobby (although we hope not). 


As a starter pond I would aim for a volume of between 500-1000gallons, obviously if you can afford a larger setup then great! Many people will say that this is too small and that you will struggle to keep good water etc Although there is some truth in what they say, for the moment, ignore them. There are many examples of koi thriving in smaller bodies of water - where there's a will, there's a way!


Not only can a correctly set up 'Mini Koi Pond' provide a great environment for your koi but it's also an affordable solution to getting involved and starting the hobby.


Prices range from around £300 for a plastic circular unit of 1100gallons, up to around £2400 for EZ-Pond's 1000gallon fibreglass tank with an infinity window. With tanks to fit every price and size bracket, they really do cater for most wallets. These figures might sound expensive in comparison to digging a hole and throwing in a sheet liner. But we are talking about building a well designed 'Mini Koi Pond' and if you consider that there is no digging, no construction and essentially no fuss - it’s actually a rather attractive prospect. Importantly, these koi ponds aren't permanent, perfect if you're just trying out the hobby! The other benefit of such tanks is that most of them come with bottom drains already fitted.


The lack of a bottom drain is THE failure of most first koi ponds! 


Shopping List.



Because our 'Mini Koi Pond' (tank) will have a bottom drain, we want a gravity fed filtration system (a filter fed via a drain). Now, lets skip another big mistake and avoid all the various well-marketed contraptions out there claiming to be good for koi pond filtration and actually install something that does the job. I think it would be unnecessary to spend money on a drum filter for a pond this size when you’re just starting out (however, you can if you wish) So, drums aside, here's my criteria for effective, manually maintained koi pond filtration:


  • The filter should be easy/quick to maintain, this will encourage regular maintenance. 

  • After maintenance is carried out the filter should be as free as possible of solid waste.

  • The filter should use minimal water during maintenance.

  • The biological capacity should be strong enough to support healthy water for koi.

  • It should be robust and fairly bulletproof  


I have two favourites for the 'Mini Koi Pond' - 


Easy pods 

- starting at £425.00 for the stand alone or £745.00 for a completely automated unit with built in Ultra Violet Clarifier and air pump. They offer a very cost effective solution to filtering a modern koi pond, plus the automated version reduces manual maintenance should you want the option. 



- The Compact unit is around £500, it's well built, simple to install, easy to clean and has a biological stage that is hard to match.

This is not a paid advertisement for these filters, the fact is that they both meet my criteria and offer great solutions for a modern 'Mini Koi Pond.' I have used both of them extensively for years on many different systems, from private ponds to heavily stocked sales tanks and it is for this reason I can recommend them. Other people may have other preferences but these are mine. 



On such a small pond all one needs is a single recirculation pump. Choose a low wattage model that will turn your pond over every hour or so and it should set you back no more than £140.00 - SuperFish Pumps are a great shout. 


Uv Unit.

Even if the tank is placed in full sun with a large window, a 25w Evolution Aqua Unit should be more than adequate at around £110. 


Air Pump.

The two filtration units I recommend will require an air pump to either clean them or for their normal operation. Either way a 70ltr model will be adequate at around £140.


Water Purification.

Koi ponds run best with a constant trickle of fresh water, a fast drip, this is the safest way to carry out water changes, dilute pollutants and replace the water lost through filter maintenance. However, the water out of ones tap needs to be made ‘koi safe’ and so a water purification unit is recommended. There are many available at various prices, but simple plug and play units start at about £70.


Pond heater.

If you can rule the weather, you can rule the world…temperature control makes keeping koi so much easier and on a small pond it won’t break the bank. A simple electric plug and play 1kw heater start at £185.00


Other things to factor in.

Pipe work, fittings and valves will be required to connect the filtration unit and other equipment, as well as a power supply and sockets for your electrical items (pump, air pump, uv and heater). 


Also think about the landscaping or overall aesthetic you want to achieve. Some stunning looks can be achieved using pre-made koi tanks. From beautiful cladding and stone work, to sunken tanks that become an ornamental feature or even utilise a fully enclosed fish house. Whatever you decide, do factor in the costs related to achieving your design. 



This is a very personal thing and in many ways it must fit with the design of your garden. But bare in mind practical things such as power supply and where your waste water will go. Also try to keep your filter and other equipment as close to the pond as possible, this will minimise long pipe runs building up with waste and will be more economical. 


The Shopping List. 

Tank (500-1000gallons - more if space/money allows)



UV Clarifier 

Air Pump

Water Purification 





Ideas on set up.


Running a 'Mini Koi Pond.'

Are there any special rules to running such a system? Not really, but smaller bodies of water will be more adversely affected by swings in water quality and temperature, thus impacting your koi. This is what people mean when they say "it's hard keeping good water in a small pond," there's less of a safety net because there's less water to 'dilute' any hiccups. But if you're vigilant and deploy some common sense, all should be well. 



Having a heater in place will eliminate one of these potential issues, small ponds heat up more quickly but they also chill quickly too. Protecting the temperature from dropping drastically and also shading the tank if you've had to locate it in a sunny spot should be enough to prevent any problems. 


Water Quality

If you use one of the filters I've recommended then biologically (once mature) they will be more than adequate to run even the largest of 'Mini Koi Ponds.' But you must maintain them. Flushing the waste from your filter is vital in keeping good water, no matter the size of the pond. 

In terms of adding fresh water, I would certainly say a water change of 15-20% per week will be beneficial. It would be good practice also, to clean your filter in order to coincide with these figures. Obviously this is just a starting point, as things like stocking levels and feed amounts will play a huge part in determining how you keep 'good water.'



If you have a 500gallon tank, a 20% weekly change would amount to 100gallons. If you filter this tank with an Eazy Pod which holds 45gallons, you should clean the Eazy Pod twice per week, this equates to 90gallons or 18%.

One could argue that if you're trickling in the 18% fresh water regardless, is there a need to clean the Eazy Pod twice per week? Could you not clean it once per week, or even once every two weeks, letting any excess water acquired go down the overflow. You're still doing the water change after all, right? 


This is true, the water change still takes place, but in my mind, if the 45gallons of water used to clean the filter for the second time is already being replaced in the weekly 18% (90gallons) - why not clean the filter? The longer waste sits in the filter, the more potential damage it can cause. Practice good habits...


Flush it - It'll be 5 minutes well spent!

Now, the same 500gallon tank with more koi, or larger koi, or exactly the same koi but with more food might perform perfectly at an 18% change per week, yet again, it might not. If the parameters are struggling what can you do without increasing the filtration? 

Reduce the number of koi.

Reduce the amount of food

Increase the fresh water and filter cleans.

So if you kept the amount of koi and food the same, you could clean the Eazy Pod three times per week which will equate to 135gallons or a 27% water change. Maybe that will keep things stable in this situation? But, maybe it won't...

The Bottom Line. 

It's not an exact science, no one can give you a magic computation that will guarantee perfect parameters, as each pond behaves differently. So it requires an element of experimentation and common sense to discover what works best for you and your pond. Always build a koi collection slowly, monitor how the system responds and act accordingly. You are a 'water keeper' after all. 


I'm not giving any suggestions as to the amount of koi to be kept per gallon for the reasons given above (I've heard so many different preferences over the years). Think of it this way, one could keep 150 little koi in 500gallons or 10 little koi in the same 500gallons, both are completely possible given the correct maintenance regime, but I think one could easily workout which koi would Survive and which would Thrive

What else might you need?

So, you're 'Mini Koi Pond' is up and running, what else do you need to ensure you can care for your koi and help them thrive in their new home.



We all have our preferences on koi food and it’s a topic that can spark quite a debate, but here are my thoughts. Buy appropriate food. If you keep and develop high class koi, buy the best food. If you keep koi that don’t fit into this bracket then buy the best quality food that suits your budget. I have always mixed my foods, I use a Wheatgerm/Staple as my base and then mix in others such as growth and colour as and when it is appropriate. This is friendly on your wallet and your water. 

Foods I personally like:

Saki Hikari 

Hikari (Wheatgerm & Staple)

Coppens (Wheatgerm & Grower) 

Kusuri (Sinking) 

Water Testing.

Whether they're chemical or electronic, start with being able to test for the required basics listed below, then see where the hobby takes you before investing in others.









The following items are needed when handling your koi.


A good quality pan net and suitable pole. 

A koi sock (one that holds water.)

A circular koi bowl large enough to hold the ponds largest inhabitant. 


Koi Health.

From time to time we must deal with parasite outbreaks or knocks that may appear, the following items are invaluable. Don't be put off by the prospect of koi health, like anything, learn the basics and you will be able to tackle most things. 

Duncan Griffiths health book - buy it, read it and then read it again. 

A microscope with slides - required in order to identify parasites.   

Koi Treatment Kit - (Scalpel, scissors, scale lifter, cotton buds)

Some people like to keep a medicine cabinet, so everything is on hand should they need it. Read Duncan's book and decide what you want in your cabinet. 

Final Thoughts.

This is pretty much everything one needs to start keeping koi in a 'Mini Koi Pond,' obviously some people have the money, space and nerve to jump straight in and build their dream pond, this article is not aimed at those people (although another will). This is intended as a starting point for those who have been led to believe that they can't have a koi pond because they don't have the space, or the budget. To my mind that really is the wrong way to look at things and frankly quite off putting for a lot of beginners. Please know...


It can be done!


Like with keeping any animal it is your duty to provide them with a suitable environment to thrive, obviously keeping koi in a well designed pond comes at a cost, but it needn't be as scary as you might think. I say it again, I'd sooner put my koi in a perfectly thought through 'Mini Koi Pond' than a larger 'garden pond' that is badly designed and lacks the necessaries. 

You can start small and learn the ropes with a 'Mini Koi Pond.'

 Get to grips with water keeping, feeding and koi health in a manageable environment. Then, when you're ready - look to expand.

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