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Top 10 Tips for Perfect Koi Keeping

Koi keeping done right

Shirley Aquatics top 10 tips for perfect koi keeping conditions. From koi food and pond plants, to ideal pond filters and pond design! Everything you need to know to make sure you’re giving your pride and koi (sorry) the best possible care. 

1.  Koi fish food – ‘Garbage in, garbage out’

An old adage from when the boss, Richard, was learning computers at school. What you put into your fish will directly affect what you get ‘out’ of them, a major consideration with koi.

There are lots of different types of food available and everything we stock at Shirley Aquatics is good quality so you will be giving your fish a reasonable diet at the very least, but there is always room for improvement. 

We have a lot of customers looking at the protein content in foods and, although that can be a useful indicator of the quality, it’s not the whole story. What really counts is the usable proteins in the food as fish aren’t able to digest everything you throw at them. Anything the fish cannot digest will be ‘returned’ to you. Albeit in a less palatable form.

Choosing a high quality food might seem an extravagance but by doing so you are giving your fish the right nutrition to ensure they produce less waste. Ultimately if you give your fish good food they will digest more of it, produce less waste, and leave less for you to clean up!

At the pinnacle of fish nutrition are probiotic foods. These can be used most of the year round meaning you don’t have to switch between wheatgerm, staple and growth diets as the water temperatures change! They also actively help the fish to digest more of their food and, well, you know the rest. 

On top of this the ingredients used in Medikoi Probiotic food also provide a prebiotic for your fish in the form of fructo-oligosaccharide! Impressive, eh? Known as FOS for short, these are short chain plant sugars that induce the growth or activity of beneficial microorganisms such as bacteria and fungi. Think of it as giving your fish a Yakult with their lunch!

So – this food provides helpful probiotic bacteria as well as benefiting the existing active population of gut bacteria and digestive enzymes. Over time this results in a vastly improved ability to absorb nutrients, increases body mass gain and massively reduces food waste.

If you aren’t going for probiotic food (and you wouldn’t be the only one) you do need to change their diet throughout the year. We recommend Wheatgerm foods for when temperatures get below 10 degrees and to stop feeding altogether below 6 degrees. Then, once warmer weather starts kicking in; staple above 10 degrees then high growth foods through the summer months. 

It’s important to note that there should not be a sharp cut off between diets, more of a smooth mixing between each stage. Given that temperature is so important to the diet of Koi, we would recommend investing in a pond thermometer.

2. Koi pond circulation

There is a lot of emphasis placed on pond filtration. However, the filter is only as good as the water you provide it with.

For every handful of food your fish consume they will give you 5 handfuls of waste – poo again, sorry! If that waste Is allowed to settle in your pond it will ‘reward’ you with a 100 handfuls of algae.  

Lucky you.

So now, rather than dealing with 5 handfuls of fish poo, your filter is having to deal with 100 handfuls of algae, and guess who has to clean all that out!

Improving circulation in your pond means those 5 handfuls of waste would quickly get transported back to your filter for processing. Great stuff. The only problem is that most of us look at the aesthetics of the pond first and rarely consider how water will move within it – this is called flow dynamics. 

The perfect shape for a pond is a hemisphere – imagine half a football. A hemisphere allows perfect circulation that guides all of the pond waste down to a central point. From here your pump can efficiently transport everything to the filter. Just like a wash basin. If all ponds were this shape, fish keeping would be a lot easier!

However, no one really wants a pond that reminds them of a toilet bowl! Instead, formal rectangular ponds are favored by most of us simply because they fit with our formal gardens and are often easier to prepare for and construct. The issue with this is the shape creates areas where slow moving water can occur and deposit waste. This occurs to some extent in all irregularly shaped ponds.

If you have the luxury of still being in the planning phase of your dream pond, consider rounding off any sharp corners in your rectangular pond, or smoothing out any sharp curves in your jelly mold design. Anything you can do to keep your water circulation as consistent as possible is beneficial.

Above the water line you can make it as formal as you like, or indeed as mad as you like, but try and keep things calm and smooth below the water line.

There are things you can do to overcome some of the challenges presented by a pond’s basic layout, such as by improving the rate of circulation. The minimum we recommend would be turning the pond volume over once an hour. The more you stray away from the pudding bowl shape the more you need to increase that flow rate to ensure you’re not cleaning up that 100 handfuls of algae.

As a real life example, Richard’s rectangular pools at home hold 5000 liters and the Pump he uses delivers 8000 litres per hour. Even then, judging by the sediment building up in the shallow areas, he may also add a second pump just to add some extra circulation. For him this is preferable to having to vacuum the pond out every few weeks.

3. Treating tap water for a koi pond

There is a reason we don’t get goldfish popping out of taps. Well, there are many reasons but this one is as good as any.

Tap water has chlorine in it. It’s there to protect us from bacteria and other microorganisms.

We’ve all been in a swimming pool which we know has had too much chlorine in it because our eyes are stinging. For the same reason it is best not to put tap water into your pond without using a suitable treatment. Chlorine will burn your fish, it will also destroy your beloved filter bacteria.

You can quite easily prevent the harmful effects of tap water by using a dechlorinating liquid commonly called tapsafe, aquasafe, fresh start, and a few others.

Despite the dechlorinating options available you cannot get away from the fact that using them is adding chemicals to your pond. In our view they are necessary chemicals produced by companies that understand fish and pond keeping, but if you’re still uncomfortable using them there are alternatives.

Water purifiers are available and at around £70 they may seem expensive, but when you do the maths, they work out at around a quarter of the price of even the most economical dechlorinating liquid. These filters often last for 10s of thousands of litres. You are also ensuring that every drop of water you put into a pond is safe. 

Some people use rainwater, which is fine, but you must take care that the water has not been standing for a long period of time as it can become stagnant. Rain water often has a low pH and if it’s been in a water butt for a while the oxygen levels will also be low. It’s worth a couple of tests before you use it. This isn’t something you need to do every time but getting an initial benchmark is important.

If you find yourself in a situation where you desperately need to do a water change, you don’t have any tap water conditioner or a water filter, and Shirley Aquatics is closed, there is a last resort. Set the nozzle of your hose to its finest setting, point it skyward and weigh it down with a brick at the side of the pond. The fine mist of water travelling through the air before hitting the pond will actively help to ‘gas off’ the chlorine, and whilst not ideal it is much better than nothing.

4. Koi pond water – Testing, testing….

This will sound like a broken record sooner or later, but water testing is vital. If everyone tested their own water it would eliminate around 70% of the problems we see. Just 10 minutes once a week could save you hours of work, not to mention expense and possibly heart ache. 

“My water is fine, it’s crystal clear!” sound familiar? There are a lot of things we can’t see that are harmful to us, so your water may well be clear but don’t assume it is safe. 

Ammonia is colourless and is one of the biggest killers of fish.

Customers who experience problems have often come to us when things have gotten really bad, and they have begun to lose fish. It’s a real battle to get things on an even keel again from that point. However, had they been testing weekly, they would have noticed conditions starting to deteriorate slowly in plenty of time and had time to act. 

If you do notice water deteriorate in your pond, water changes are often the best solution. Throughout this process you should test daily and change water if necessary. 50% water changes (or even bigger!) may be needed if the water is extremely bad and this needs to be repeated regularly until conditions get considerably better.

kH is not something most people consider. It’s the carbonate hardness of the water. Birmingham is a soft water area and not paying attention to the hardness in your pond can result in pH crashes which in turn cause your filter to crash. 

If you want to know the hardness of your water Aquacure have this very useful tool for checking the water hardness for your postcode alongside this handy map – the darker the blue the harder your water.

Without doubt, if you live in a soft water area, you should be buffering your pond regularly to prevent issues sneaking up on you. The minerals a buffering solution provides are just as important to the filter bacteria as they are to the fish. 

Everything that breathes underwater produces dissolved carbon dioxide. Your fish do it, your filter does it, bacteria do it, leaves rotting in there over winter (shame on you, get them out of there), even submerged plants at night time. Dissolved Co2 in water forms carbonic acid and this acid erodes the hardness of your pond water. Quite literally, everything is working against you here!  

KH is a test that takes 30 seconds and, again, will mean you and your fish are a lot happier in the long run.There are many buffers available but the one we use is the incredibly economical KH Mineral Additive.

5. EcoTreat Clarity

Regular readers of our knowledge base articles will already be familiar with the wonder that is EcoTreat Clarity. 

Any pond project should factor in the use of EcoTreat Clarity. It adds beneficial bacteria to your water that outcompete algae for sources of phosphorus or nitrogen, meaning clearer water and no algae. Not only this but that very same bacteria will digest your sludge and waste. It’s also not very expensive! Rather than waffle on – here’s the key bits of information useful to you.

It’s not just a natural pond product, it’s not just a garden pond product or even a Koi pond product, it is perfect for all ponds. We have some of the best filtration systems on our koi section, and still find it an invaluable tool for reducing waste, improving clarity and preventing algae.

Is Clarity the perfect product? 

  1. Less waste and sludge – meaning less work for you and your filter!
  2. No algae – including the dreaded blanketweed!*
  3. Biological supplement and pond water conditioner – redresses any imbalances
  4. Economical – a small tub of 250g costs £7.99 and will treat a small pond (less than 2500l) for up to 6 months
  5. No harsh chemicals – a natural product.

*if you’re currently struggling with blanketweed and need some advice, read this.

So yes, it is the perfect product. It’s an absolute no-brainer for us. Get some.

6. Pond plants – Plant for perfection. 

Plants make our gardens something special. They allow us to express ourselves, surround us with colour, and filter our air. 

They make a pond something special too. 

However, Koi also love plants. Think of them as a load of toddlers presented with a nice full toy box. They are going to try and chuck everything out and destroy all of your plants. If you are going to introduce lilies use cobbles or other methods to ensure they can’t get at the top of the baskets.  

If you have a shelf, it’s the perfect place for marginals, but make sure it’s shallow enough for the koi not to get their little piggie noses onto the baskets. You can raise baskets up with house bricks or again use cobbles to shield the plants. Marginal pond plants are recommended at around 50cm intervals around the circumference of your pond. They look great, absorb nutrients from the water, and some, like watercress or nasturtiums, are even edible!

If you haven’t got a shelf, there are options, floating baskets, overgrowing matts, even using the wire from a metal coat hanger to hang baskets over the side, there are lots of ways to go green with your pond. In a good way. Considered planting will, in turn, help to prevent your pond going green. In a bad way. 

If you’re at all unsure about what plants to buy, what your options are, or where to even begin looking check out our Ultimate Short Guide to Pond Plants.

7. Pond filter – keep it clean!

This one is short and sweet.

You should be cleaning your filter once a week in the height of summer, once per fortnight in spring and autumn, then once per month over winter. 

Once more for the people in the back.

You should be cleaning your filter once a week in the height of summer, once per fortnight in spring and autumn, then once per month over winter. 

Little and often is the key. It will take a lot less time if you are cleaning regularly. Also, don’t forget that your filter media must not touch tap water. Use water you’ve removed from the pond to do your cleaning. Many filters have a cleaning mechanism to make the process even easier. Some will even do it for you.

Third time’s the charm…

You should be cleaning your filter once a week in the height of summer, once per fortnight in spring and autumn, then once per month over winter. 

8. Pond oxygenation – it’s not just a load of hot air.

When the weather is cold you need to limit the contact between your pond water and air. You should be bypassing waterfalls, turning off fountains etc. The reason for this is your fish’s respiration drops significantly at these times, so they don’t need as much oxygen. In the warmer months the opposite is true, so you need to maximise the mixing of air and water by turning everything on full. Even then, it sometimes may not be enough. 

Adding an air pump in summer can, without doubt, save lives. It injects much needed oxygen into the water. It also disturbs the surface of the water. This increases the overall surface area meaning a higher rate of gas exchange. Imagine the surface water as the ‘gills’ of the pond – releasing carbon dioxide and other gas pollutants, and taking in oxygen. (This is one of the major reasons you shouldn’t let your pond completely freeze over in winter, too.)

You can, in some cases, add air to your filter to increase biological filtration, some filters such as the easy to clean EAZYpod come with an air pump, which you can use in your pond for 90% of the time and use it to clean the filter when the time comes.

It’s also a handy backup if ever your main pump packs up. And you can pretty much guarantee this will always happen at the worst possible time. Solar air pumps are also available and can be extremely useful as they have all the benefits of a standard air pump, but can also act as a safeguard in the event of a power cut.

9. Preventative measures

Parasites can arrive in your pond via a number of sources, including birds and amphibians. You will often have a resident, background level of parasites in the pond that the fish tolerate, until a stressful situation occurs. Stressful situations from a fish’s point of view include the introduction of new fish, a lot of temperature changes, or poor water quality. 

At this point the population of resident parasites increases above that tolerance threshold and gets out of control, harming fish in the process. We recommend doing a preventative treatment of something like Eradick (an anti-parasite and anti-fungus treatment) in spring and autumn, as well as following the introduction of new fish. This reduces the background level of parasites in your pond, giving the new fish a chance to settle in. 

We understand that people may have an aversion to putting chemicals in their pond. However, it’s worth considering that we, as people, take preventative treatments (multi vitamins, probiotic yogurts etc) all the time, and when we get sick we take medicines (paracetamol, antibiotics). It’s the same principle with fish, only they can’t tell you when they’re feeling sick so it’s often best to be proactive!

Koi are mostly like bulls in a china shop, but instead of delicate bone china this shop is full of spikes and steel plates. They’ll still charge around like they’re invincible. They get knocks and bumps and scrapes all the time. You really need to pick up on these and apply treatment directly to these marks. 

Propolis is a very good natural antibacterial treatment that should be applied topically to wounds. If you don’t act on these bumps and scrapes they are likely to get infected by bacteria, then fungus and even algae. From there the wound will get bigger and bigger and then suddenly you’re calling out the vet. Nobody wants that. 

10. Koi pond protection – the winged terror!

They’re amazing, majestic creatures and they are one of our biggest native birds. They are also complete gits!

Our final tip is about Herons. We regularly hear stories where they have cleared customers’ ponds of fish. Or, perhaps worse, have skewered a prize koi but been unable to carry it away, leaving it to die on the side of the pond. They are a pest, just like your neighbour’s cat that defecates on your lawn but, unlike Tibbles, Herons are a protected animal. 

They are also incredibly clever and use numerous tactics to attract fish towards them. It often feels like they are holding all the cards! The best form of defence is a physical barrier, i.e. a net, canopy or pergola. Whilst these can often be unsightly or difficult to build, they may be your best options.

Having said that, it’s worth exploring the other avenues. Netfloats are circular or rectangular lightweight grids that you can secure together and place around the edge of your pond. They act as a physical barrier but do not need to cover the entire pond. They float at the surface, but (much like the obstacles when going on a bear hunt) the heron can’t stand on them, can’t fish through them and can’t fish over them. They can be very effective and are used by Richard on his home ponds.

Heron decoys are a favourite but it bears repeating, these birds are clever. If they see the same “bird” standing in the same place day after day, they are going to smell a rat. Take a few minutes to move the decoy heron around the pond regularly. 

You can also use wire fences that run around the edge of your pond, there is also an electric version which does work extremely well. Herons like to wade into water, so if they have to step over something into deeper water they are more likely to give it a miss. It is worth noting that from their bird’s eye view they can easily spot a body of water. After a successful effort a heron will return until the pond has been fished out so assume you are going to get a visit from a Heron on your new pond and plan accordingly. 

There you have it for our Top 10 Tips for Koi Keeping! If you have any questions about any of the points above, or think we’ve missed out something crucial let us know!

If you’re at all curious about how it’s done across the pond (sorry, again) then Hermann Samano of has this to say about How to Build The Perfect, Peaceful, Backyard Koi Pond.

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