How To Clean A Koi Fish Pond

A question we get asked all the time is how do you clean out your pond, and keep the water clean and clear.

The answer is…

It depends.

Read on.

Koi ponds by their very nature are dirty places. Fish load, the amount of food you feed your fish, and the surrounding area all give rise to dirty pond water.

Some of the points we are going to cover today that effects pond cleaning is as follows:

How the pond is set up?
How do you remove debris and sludge from the bottom of the pond and is there a way for you to drain the water?
Is it a new pond?
How many fish are you stocking, and what type?
Where is it positioned in the garden – very important this one…

These questions are just a few that we need answers to before we can come up with a plan for getting you that crystal clear look you always wanted in your koi pond so you can admire your fish all year round.

One thing for sure though is no matter what, we would never recommend fully draining your pond when cleaning it unless you have suffered a catastrophic failure or contaminated the water beyond repair.

How often do you have to clean a koi pond?

If you have everything set up correctly you should never really have too much work to do with cleaning your pond to keep the fish happy and the pond clean.

Let's consider an ideal scenario where you planned everything out from the very start and built the ideal pond.

First up you would have installed an aerated bottom drain and a gradually sloping base in your pond to remove all the waste and muck from the bottom of the pond.
Next, you would have installed a skimmer to remove any surface debris and keep a nice polished look on the surface of the water.
You would have installed some mid-depth TPR's in the walls of your koi pond – that is at least 3 foot deep to help circulation.
You would have a pump strong enough to completely turn the water over in the pond every hour.
A multi-stage filtration system for mechanical and biological filtration.
A UV clarifier to keep green algae at bay, connected via a hose back to your filter.
Finally, a bog-filter to filter fine particles and nutrients from the water before it is returned to the pond.

See, that's not how life works.

Most of us when we get around to building our first pond dig a hole, throw in a liner – either rubber, PVC, or solid plastic liner, fill it water, and chuck in a few fish. A week goes by and then because it looks so great you go and buy another handful of fish and in they go too.

Another few weeks go by and your lovely clean pond water is not so clean anymore.

At this point, people start to panic and head off to the shops and buy all sorts of chemicals to clear up the water. The reality is all ponds suffer from what's commonly known as 'new pond' syndrome.

This is where your gin-clear water turns a nice shade of green. You can no longer see your new koi or fish because the green mirky water is everywhere.

So what should you do?

First up – don't panic.

This transition is perfectly natural and happens to every new pond.

The order of where we would start goes like this.

Pump – Keep your water moving

Priority number one on any pond is to circulate the water and keep it moving. Still water goes stagnant and will kill your fish.

On small ponds, you often see a small in-pond fountain splashing on the surface. While not the best thing for keeping your pond clean – it's better than nothing.

How to clean a koi pond

We will also add aeration to this section. Adding air to your water helps a huge amount in the overall health and condition of your pond. Having aerated water is great for your fish and keeps everything in the koi pond moving.

You may do this with a pump-fed waterfall of even by adding a small air pump and some airstones to the pond or if you are lucky enough to have installed an aerated bottom drain.

Filtration – Removal of waste

The first thing we always look at is filtration. How are you removing the fish poop and muck from the pond? If you don't have a bottom drain that gravity feeds your filtration then you are most likely using a pump to get the water from the pond into a filter.

The filter itself needs to be big enough to cope with the waste load from the pond and starting out people either make their own from YouTube videos or buy a purposed built filter.

Both have their merits and both can do a perfect job if they are set up correctly.

my diy filter for the pond

A pond filter is the best way to keep your koi pond clean. Koi produce lots of waste and a good filter will house enough bacteria to remove most of the waste from your water and keep things balanced. Read more about my DIY pond filter.

Plants act as natural filters and also reduce nasty chemicals and improve water quality.

Beneficial Bacteria

All ponds are full of bacteria – both good and bad.

On a new pond, you will need to jump-start the filter to get it performing properly. Adding some beneficial bacteria at this stage is the right thing to do. It's this bacteria that helps remove the nasties from the water. Koi produce ammonia. Dead and decaying waste on the bottom of your pond also produces ammonia. The breakdown of this ammonia causes nitrites in your pond.

Adding beneficial bacteria to your pond consumes these nitrites and helps keep your pond balanced.

We are not big fans of removing lots of your water from the pond but if you are suffering from high nitrite levels then the only way to combat this is to perform a 25% water change with de-chlorinated water.

Pond Skimmer – Surface Debris Removal

If you think about your koi fish pond for a second. Everything that goes into the pond has to enter via the water's surface so it's a great place to start when it comes to cleaning it.

A pond skimmer will save you a lot of time in the long run, help keep it clean, and really cut down on overall pond maintenance.

Put it another way – if you can catch any debris that enters your pond before it sinks to the bottom will save you all sorts of work later on trying to get it back out again.

Depending on where you located your pond you are inevitably going to end up with leaves, twigs, and other unwanted rubbish in the pond water. A skimmer will help remove this before it sinks to the bottom and starts to rot away.

There are three main types of skimmers for pond cleaning.

Skimmer Box

A wall-mounted skimmer box that is plumbed into your overall system sucks water from the surface of the pond and off into your filters for cleaning. These types of skimmers have a removable basket that collects all the leaves and dead bugs etc for handy removal.

The downside of these is they require a bit of planning before you build your koi pond.

Floating Skimmer

If your pond is already up and running and you don't have the option for a wall-mounted skimmer, then you could opt for a floating skimmer or submerged surface skimmer. Both of these options are easy to set up after your pond is completed as an add-on.

Both these skimmers can be added using a separate pump that pulls water from the surface of the water down through the skimmer and simply returned back to the pond. Nothing too complicated about this setup. They are designed to just remove surface floating debris from your pond.

A final note on skimmers is to make sure that if you have floating plants in the pond then separate them from each other. They will really help clean the pond but will suck up anything floating on the surface of the water.

The final option you could employ here is to invest in a decent pond net. Go for one that's sturdy but with a fine enough net mesh to help remove smaller bits from the pond.

UV Light – Remove Green Algae.

We mentioned green water earlier when discussing new pond syndrome. No amount of cleaning or scrubbing will remove algae from the water. A great way to combat this problem is to pump the water through an ultraviolet clarifier that will kill off the cells that cause this green water. These microscopic cells multiple very quickly and it may seem like your pond turns green overnight.

The algae itself causes zero harm to your koi pond- if anything the fish like it because it provides cover so they can swim about without anybody seeing them – but that's the problem – you can't see your fish.

adding a UV clarifier to your pond will help reduce green algae

Algae blooms happen all the time and apart from when your pond is new, it's a sure sign that the water balance is off somewhere. This may be because of too much direct sunlight or an abundance of extra nutrients in the water.

If your pond is in full sunlight then a good method to combat algae growth is to introduce some plants. If you want to remove larger free-floating clumps of algae then one step would be to net this out of the water.

Both floating plants like water lettuce and using potted plants like Lillies and Iris will provide shade from the sun, giving your fish somewhere to hide, plus they eat the excess nutrients and bad bacteria from the water. Plants are easy to manage, natural filters, and as long as you keep them in check they are the best method to make healthy happy koi ponds.

Everything mentioned above is either a natural or manufactured process to clean your pond. You may think that draining your koi pond is the only way to keep it clean, but koi ponds, in general, are never 100% clean, but that's why they work.

How do you clean a koi pond without draining it?

With the right setup, you can manage and maintain a clean healthy pond without ever draining it out. The reality is if you do drain it you are nearly starting again because you will kill off any beneficial bacteria growing in the pond that is helping to maintain the ecosystem and balance of life.

A koi pond takes time to mature, the pond water needs to cycle and the bacteria need to grow in your filter system. Make sure you let things settle down, get the pump flow through the filter system tuned, and add in a skimmer for surface cleaning.

How do you clean a pond without killing the fish?

Cleaning your pond involves a bit of work. You need to remove as much sludge from the bottom of the pond as you can using natural options like a net or pond vacuum. Avoid draining it at all costs. Put the effort in and use natural elbow grease instead of harsh chemicals

You should clean your pond whenever necessary but as mentioned the best time to do it is the end of autumn to get it and the fish ready for the winter, or when things heat up a bit in the spring and the fish start moving about again looking for food.

When should I clean my pond?

Work out a maintenance plan and aim to do your major cleaning either at the start of spring when the water starts to heat up again and the koi become active, or towards the end of fall when things start to slow down again.

Make sure everything is done before winter sets in because the koi will slow down, and your plants will die back. Take as much sludge out of your koi pond by cleaning the bottom debris and dead plants – you might have access to, or invest in a pond vacuum to clean the pond or large fine net at this stage to help with maintenance and debris removal.

Whatever you do, once winter sets in, leave your ponds alone. The combination of cold and reduced immune systems in your koi means they will not recover from a shock if you drain the water in the pond or perform a large water change. Fish need little or no food once the temperature in your ponds drops below 10 degrees so it's a good time to leave everything alone.

fish will stay in deeper water when winter sets in and ponds freeze over.

If you have a bottom drain then turn off the pump and flush the system out with a hose if you want to remove any large debris and settled sludge from the pipes. Get rid of the last of the sludge with a net on a long pole.

Put your plants in place at the lowest part of the pond to protect them from the cold.

When winter kicks in you will be glad you made the effort to clean the koi pond. Removing all that sludge improves the overall quality of the pond water and reduces the risk on your koi when water temperatures drop or the pond freezes over.

At any stage, during the year you should clean away and trim back overgrown foliage and surface plants so you can view and admire your koi or other fish.

Scoop out the sludge whenever you notice a buildup in the bottom of your pond or after an algae bloom has died off

How do I make my pond water clear naturally?

If you want a natural pond and do not want to use any artificial cleaning methods then you could use a natural bog filter to remove debris waste from the pond. The bog filter acts as a cleaning sieve and will improve water quality over time. You pump the water from the fish pond up via a hose into the bog and let it flow up through a bed of gravels that remove small particles and floating sludge from the water. Once you introduce plants to this type of filter they will thrive and produce strong root systems that remove waste and are very beneficial to your pond.

Once they get established around ponds they provide a haven from good bacteria, need little or no maintenance, and can drastically improve your water quality.

A good bog filter has many benefits and once in place and established one may provide better filtration than any manufactured solution on the market.

They do take a while to get established so a first step may be to use a biological filter while the plants take to the conditions.