Can you protect your koi pond from herons?

heronThere is nothing more soul-destroying than an heron visiting your koi pond. Your fish will start disappearing rapidly as these skilful and determined thieves work out how to bypass your protection measures to access one meal after another. You will soon understand that the term bird brain is a misnomer. Herons are clever – very clever!
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Is soft water better for koi?

koi carpSome koi keepers have alleged that soft water is better when keeping koi. They believe that very soft water encourages enhanced growth and improved colour development. But they are wrong! Freshwater fish, including koi, should be kept in stable conditions and in water with a PH between 6 and 9. The degree of hardness should be no lower than DH6.

The degree of hardness is made up of two factors – KH and GH. KH is a measure of temporary or carbonate hardness and GH a measure of the total dissolved minerals in the water. GH is hard to change whereas KH can be altered relatively easily, both intentionally and accidently.
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Your Koi Pond in Spring

koi pondWhen spring arrives and temperatures begin to rise, your koi will become more active. It is important that conditions in your pond are perfect for your fish and that you feed your stock correctly as they emerge from their winter fast. Here are our top tips for a heathy pond in spring.

Monitor the water temperature

A floating pond thermometer is a must-have accessory. If you don’t have one, invest in one today! Koi are cold blooded and so cannot regulate their own body temperatures. Their behaviour will be dictated by the water temperature and so it is vital that you know what that is. Your koi should start to become active when the water reaches 50–55F and it is important that you don’t do anything until the water is stable at this temperature.

Koi pond cleaning

If you have rocks at the bottom of your pond, you may need to move your Koi temporarily and clean the pond before you start treating the water and feeding your fish. Debris caught between rocks will impact the water quality and your Koi’s health. Consider removing the rocks as they result in annual disruption for your fish which isn’t beneficial for their wellbeing. The rocks could impact the health of your stock even if you clean your pond every year.

Treat your pond

After a winter of fasting, your fish will be weak and their immune systems vulnerable. It is crucial to attend to any parasitic or bacterial issues before you start feeding your stock. Treat your water with an antibacterial product such as Pond Doctor Anti Bacteria but take care to add the right amount for the volume of your pond.

Activate your filter

Whether you are using a mechanical filter (beads filter) or a biological filter, you may have stopped filtration during the winter. If you did, you need to restart the nitrogen cycle. Clean inside the filter and add beneficial bacteria to the filter or the pond.

Be patient in feeding

Feeding your koi is enjoyable and so you will probably be anxious to get on with it, but don’t rush! Your koi may not be quite ready, even when you have perfectly prepared your pond. They are emerging from a long fasting season and will be hungry but weak and so their bodies are not in a condition to eat their normal diet.

Begin by feeding soft and highly digestible food. You could soak some pellets with water and then feed these to your fish. But this could cloud your pond water, so take care. Alternatively source a digestible food formulated for the season and feed this once every few days to begin with. When the water temperature is consistently 55F or above, you can feed your regular koi food once each day.

Consult the feeding guide of your chosen food and increase the amount you feed your fish as the water temperature rises.

Koi stolen from Yorkshire pond

These days people will steal anything if they think there could be a few quid to be had and that includes your fish! To make matters worse, those targeting koi can be well-organised and efficient. Your fish can disappear without you sensing anything is wrong and that is exactly what happened to David Hobson.

Bedbound enthusiast loses entire collection

David Hobson is 74 years old and bedbound. He had built up an impressive collection of koi over 30 years and more. His family grew up with the fish and they were his pride and joy. David’s collection featured 35 koi worth between £25,000 and £30,000 but they have all been stolen.

Garden pond raided

The fish were taken from a pond in Mr Hobson’s back garden in Baildon, Yorkshire. Thieves took all of the koi specimens, leaving only a couple of goldfish and two mirror carp behind. The house wasn’t broken into and so the thieves had clearly targeted the fish and must have known they were there.

A great hobby for a man in pain

David had become a keen fish keeper as he suffers from arthritis. The pain caused by his condition prevented him from engaging in many activities but he could manage looking after the fish. Unfortunately, he recently suffered a stroke but his family have helped to keep the pond well-maintained and to care for the koi.

The koi boasted a mixture of colours and patterns and the collection was impressive. Following news of the theft, fellow enthusiasts posted expressions of sympathy on social media and some even offered David specimens from their own collections to replace the missing fish.

Protective net removed and replaced

David’s koi had been covered by a net which had been attached to the pond to prevent birds attacking the fish. The net had been unfastened, pulled back and replaced over the water during the theft, all without anyone in the house hearing a thing.

Will the fish survive?

Looking out of the window at the fish had been an enormous comfort to David who had become bedridden after the stroke. He had invested many hours in building the pond and 30 years nurturing the collection. He built everything from scratch, but all of his fish disappeared in just one night. He couldn’t believe that they had been stolen and is concerned that the trauma of being removed might kill them.

Pond security

If you have a koi pond, what can you do to prevent your fish from being stolen? In practice, it is very difficult to stop a determined thief. Obviously, locked gates are a must and it is best if your collection isn’t common knowledge. You should install floodlights with motion sensors as these may deter some intruders and if you can afford them, security cameras would be a good investment. Cameras may not deter all thieves but they might make it possible to identify them after the fact.

Even fish can get sunburnt!

Koi by Hellsgeriatric (via Flickr)
Koi by Hellsgeriatric (via Flickr)

You might be surprised to hear that fish, including koi, can suffer from sunburn.

How could this be?

Water does provide a barrier to UV rays but middle and long UV wavelengths can penetrate water for a few centimetres, especially if the water is very clear. Which it would be in a koi pond! Koi wouldn’t normally choose to spend too much time near the surface of the water but may be forced to if the water is too shallow or they are struggling to get enough oxygen from it.

Coldblooded creatures

Koi are coldblooded creatures which means that their metabolisms speed up as the water temperature increases. They then require more oxygen but the oxygen available will be decreasing as the water gets warmer. The struggling fish move to the surface and become vulnerable to the UV rays. Fish may also move closer to the surface of the water if the pond is overcrowded.

Symptoms of sunburn in Koi

Fish may develop skin sores in the areas exposed directly to the sun including the top of the head, dorsal fin and upper back. The affected skin will first turn whitish in colour and then eventually becomes patchy, thickened and creamy. Fins will become frayed and as the sores develop, the skin flakes off leaving a whitish or pink coloured ulcer.

In extreme cases, sunburn can result in serious imbalances in the blood and then kidney damage. Bacterial and fungal infections may develop and these might mask the original lesion, concealing the root cause of the problem. If you spot lesions in hot weather, always consider the possibility of sunburn. These secondary infections can be more serious than the original sunburn. Most fish will survive a case of sunburn if cared for properly but will often be permanently scarred as a result of their ordeal.


Certain chemicals can impact photosensitization in fish which means that the effects of the sun will be increased. If anything is to be added to the pond water, it is worth checking the photosynthesising properties of the substance before using it.

How to protect Koi from sunburn

It is important to ensure that your pond isn’t overcrowded as this will cause an excessive demand for oxygen. If you’re your pond is shallow, deepen it if possible. Avoid contaminating the water with photosensitizing agents and top up the pond with cooler water if it is overheating or evaporating too quickly.

You should check that your pump is working correctly and provide shade over the pond to protect it from direct sunlight. Better still, fit a koi shelter in the pond or construct a cave to provide a refuge for the fish.

If your koi have become lethargic in hot weather or appear generally unwell, they may be suffering from sunburn. In addition to the aforementioned preventative measures, consider the use of a fish stress reducer to help restore your stock to good health.

Frogs and toads in decline as ponds fall out of favour

In addition to providing an attractive feature for your outside space, a garden pond is incredibly important for wildlife. But fewer gardens feature ponds these days and the inevitable consequence has been a decline in the number of frogs and toads in Britain.

frog sitting on a log in a pond

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8 ways to kill your koi

koi carpKoi keeping is an increasingly popular hobby. The fish are fascinating and provide a colourful addition to any garden. But while koi are hardy fish which are well-adapted to living in a variety of climates, they do have specific needs. If you are new to keeping koi, it is easy to make mistakes and to fall short of meeting the basic needs of the fish. Here’s eight ways that you could kill your koi.

  1. Pesticides
    We know that you wouldn’t deliberately pollute your pond with pesticides. However, in heavy rain, runoff can find its way into your pond water and bring pesticides from the environment with it. It is important to allow for this fact when planning the construction of your pond and you may need to create a means of diverting runoff away from it.
  2. Infections
    Koi can fall prey to viral or bacterial infections. They can generally fight these off but it is important to maintain good water quality and to provide your fish with the correct diet. Keep an eye out for signs that your fish are unwell and act quickly if you have concerns.
  3. Jumping
    Koi are natural athletes and may even appear to be suicidal at times! They can and do jump and if they miss the water on the way down, they could perish before you discover that there is a problem. If one of your fish is a persistent jumper, installing a bird net might be a good idea.
  4. Lack of oxygen
    Keep an eye on the growth of your fish because competition for supplies is the most common reason for oxygen deprivation. You should stock your pond with the correct number of fish for its size and consider featuring plants to boost oxygen levels. As the fish grow, their oxygen consumption increases. A nicely balanced pond environment can soon become a dangerous one for your stock.
  5. Predators
    Your fish represent an inviting meal for predators and they will be persistent in their attempts to get it. You will probably need a bird net and fencing around the pond. If you don’t protect your fish you will soon find them disappearing. Once a predator has found out how to access your pond they will keep coming back.
  6. Ulcers
    Koi rest on the bottom of the pond in winter and so their undersides are in contact with any substrate. Their bodies could become ulcerated as a result and so it is best if the bottom of the pond is smooth.
  7. Parasites
    Koi can be afflicted by parasitic infections. Unfortunately, by the time the koi exhibit visible symptoms, an infection may already be severe. Most infections are easily treatable so the key to success is to carefully monitor the fish for signs that they are failing to thrive. Look out for listless fish, koi which have lost their vibrancy and individuals which will not eat.
  8. Poor Water Quality
    The number one cause of koi death in ponds is poor water quality. Always ensure that your filtration system is working well, regularly test your water and don’t overstock the pond.


Can you grow plants in your koi pond?

koi carpThe short answer to that question is only if your fish will let you! Large koi may demolish or eat your plants but adding plant life to your pond is beneficial for Koi. The plants will also lift the look of your pond and transform it into a more beautiful feature of your garden.
But you need to choose the right plants and place them correctly so that they are not quickly consumed by the fish.

The benefits of aquatic plants in a koi pond

Aquatic plants are considered to be good additions to any koi pond. They help to increase oxygen production in the water and they keep the water cooler in hotter temperatures whilst creating shade for the fish. In spring, submerged vegetation provides a surface on which female koi can attach their fertilised eggs.

Plants also prevent the spread of algae as the shade they provide limits photosynthesis. Plants create a natural filtration system which restricts the formation of blanket weeds.

How to introduce your plants

The best way to introduce plants into your pond is to build a plant shelf. This can be constructed
along the edge of the pond. You should weigh down the plants with large rocks or stones as this will form a barrier between the plants and the fish and so restrict the number which are eaten! Do be aware that the plant shelf might make it easier for predators to feed on the fish and so preventative measures may be required to protect your stock

Floating plants, shallow-water marsh plants and submerged plants can also be placed directly into the pond.

Floating plants

Floating plants feature vegetation which sits on the surface while the roots hang down in the water. With some species, the roots may attach to the bottom of the pond. These plants provide shade for the fish and are generally easy to care for. Consider featuring water hyacinth, water lettuce, water lilies or lotus. Keep an eye on the growth of these species as they can get a little out of control.

Shallow Water Marsh Plant

These aquatic plants are typically planted on the edge of your pond in the shallow water. Consider water iris and horsetail for your pond. Umbrella is also an option but will not survive a harsh winter.

Submerged Plants

These species are grown in pots and then placed at the bottom of the pond. They are great oxygenators and remove excess nutrients from the pond environment but may be uprooted and eaten by the fish. Fanwort, American waterweed and water Purslane are good choices.

You might have to experiment to see what really works in your pond. With a little planning, you should be able to plant your pond so as to improve the water quality for the fish while also creating a more attractive look. You never know, you could discover a passion for gardening as well as for koi!

A new kind of car pool

A little research will reveal all the advice you need to create a koi pond for your home. As we have explained on this blog, size matters and it is important to ensure that you can maintain good water quality.

Most people choose to build their koi pond using bricks or cement but one enthusiast has taken the unusual step of using a car!

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Japanese koi accidentally dumped on campus lawn

Japanese koi are associated with good luck and prosperity. But there wasn’t a great deal of good fortune about when a consignment of koi was delivered to a Chinese University recently.

Linyi University in Shandong province had been offered a donation of 13,000 live fish by a fishery firm. The consignment of fish was duly sent to the university and included some 3,000 koi. Unfortunately, disaster struck when the delivery was made. Continue reading “Japanese koi accidentally dumped on campus lawn”