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How to move your pond fish safely when moving house.

by Ben Helm*

Moving house (along with bereavement and getting married) is widely regarded as one of life’s most stressful experiences. There can be so many unpredictable variables that appear to conspire collaboratively to complicate the process, testing our patience to the limit.

Any typical house move will require meticulous planning to make sure that if nothing else, all of our earthly belongings can be moved safely between properties. The more fortunate ones can leave the packing and moving to professionals who have vast experience at easing wardrobes down flights of stairs and packing the most fragile of items so that they arrive intact at their destination.

Those of us with children can be faced with additional challenges (depending on the distances involved) while pets can add even further difficulties along the way. And if those pets are koi, we can be faced with making a host of complicated arrangements – Something that cannot and should not be left to the moving professionals.

Each house move will be unique with respect to its specific details, but when koi (or any pond fish) are involved, a number of steps need to be planned to make the move as hazard and stress-free as possible for our koi and ourselves.

Moving and Stress

Incidents of disease will lag behind periods of stress. When koi experience unfavourable and extreme changes to their environment, they will inevitably suffer stress. This could involve a rapid deterioration in water quality or repeated netting and handling, either of which are likely to be experienced during a house move. When koi experience such changes, their bodies react in such a way as to make them more susceptible to disease and it is our responsibility to plan wisely and as best as we can.

The move can be split into 3 stages: Preparation, transportation and acclimatisation, and by managing each part individually, steps can be taken to keep stress to a minimum.

large fish being carried in sling under frame

Preparation – Before the move

Professional breeders prefer to move koi in cooler temperatures. The Environment Agency (the government body that is responsible for the quality of our waters and the life that they support) prefer to move and survey fish either side of the warmer months rather than handle fish in the summer time. At cooler temperatures, fish metabolism is reduced and because they are less active, they are easier to catch. Furthermore, where the transportation of koi is involved, they are better off transported in cooler temperatures as their demand for oxygen is reduced yet the water’s ability to hold oxygen is increased. Consequently, you can transport more fish, for longer periods in greater safety.

Unfortunately, during a house move we cannot choose to move our koi ‘out of season’ as our timing is dictated by estate agents and solicitors. But we can learn a few principles from the professionals and apply them where possible to our own move for the benefit of our koi.

  • Feeding. Plan to reduce feeding as the date of completion approaches (especially if it is a summer move). Koi excretion rates increase with stress, leading to the fouling of the transport water. Koi can quite easily go without food for a week and this will allow them to evacuate their guts prior to the move.
goldfish in plastic bag Water for transport. Netting and capturing koi can cause any settled sediment or debris to be resuspended in the pond (especially in a planted pond). If this water is used for transporting koi, the suspended particulate matter will make the water inferior compared with clear and debris-free water.

Water for bagging should be collected from the pond before netting starts, ensuring that they get the best water for their journey.

Planning transport. Professionals that work in the fishery industry transport their stock in fibreglass tanks (approx 1 cubic metre) that are sited on the back of a pick-up truck. These tanks allow fish to enjoy a greater volume of water during transportation as well as the benefits of vigorous diffused aeration. Unfortunately, unless you have a willing contact in the fishery industry, this preferred method of transportation is not an option for house movers and you will have to rely on the way in which your koi entered the country – in polythene bags. Available from koi dealers, large clear bags and elastic bands are essential for moving koi.

A helping hand. Netting and bagging a collection of koi can be a lengthy and risky procedure and should be carried out as quickly and as cautiously as possible. Chasing koi around a pond will only stress all fish involved and lengthy periods of time spent in a bag while other koi are caught should be avoided. If koi are bagged soon after a prolonged ‘chase’ their rapid respiration rates while they recover will soon deplete the bagged water of oxygen. Ask a friend who you can work with in a team to shepherd and net fish calmly and efficiently one at a time. They can also help with the bagging up and carrying of bags to and from vehicles.

Transportation – The Move

A useful piece of equipment that can make life easier for you and your koi is a large floating cage net. Your koi can be netted at leisure and deposited into the floating cage, and then, when your bags and assistance is ready, the koi can be lifted swiftly into the bags, ready to be transported.

If possible, oxygen should be used to inflate the bags with the majority of the bag’s volume taken up with oxygen and the remaining 20% with koi and water. Bags should be double bagged to give extra protection against leaks and placed in either a box or a bin liner to cut out the light and hence reduce koi stress.

Risks involved in transporting koi

By identifying the potential hazards when transporting koi, we can ensure that the risk of the hazards occurring can be kept to a minimum.

  1. Damage and abrasions to koi during netting. Koi can be spooked quite easily, inflicting damage on themselves by swimming into pond sides and pipework. Localised damage can often go unnoticed only to develop into an ulcer days later. The last thing you want to see is an explosion of loose scales floating through the water as you net your koi as this is a sure sign that the koi will have damaged themselves.
  2. Koi will readily leap clear of the pond if chased too vigorously. It is virtually impossible to out sprint a fish, netting it from behind, and in trying to do so will cause a koi to leap out of the water to escape its perceived predator. Avoid at all costs causing koi to race and speed up in a pond, but net them head-on by guiding them gently into a net. Two netsmen makes this so much easier.
  3. Deterioration of water quality within the bag. Even though koi will spend tens of hours in a plastic bag when exported from Japan, even 5 minutes in a bag is stressful for koi and their time spent in a bag should be kept as short as possible. Stress increases a koi’s respiration and excretion rates, both of which will cause the water in the bag to deteriorate. This is why the use of a large transport tank is far better. By assembling all of your koi in a floating cage net prior to bagging, you can keep the time that koi spend in a bag to a minimum.


To be realistic, moving house is likely to involve two moves for koi. As most moves involve leaving your old house and moving into your new house in a day, there is no scope at all for preparing a suitable pond at the new house, especially as one will probably take 4 weeks or so to start perform biologically. You may, as part of the sale agreement, be able to negotiate that your koi stay where they are for a month or so, giving you at least an opportunity to set up a temporary pond for your koi. This is only practical if you are not moving far and are allowed frequent, unhindered access to your fish and filter system.  

Alternatively, instead of being transported on the day of the move to the new house, they could be boarded at a friend’s pond until your temporary or new pond is in a suitable state to receive koi.

Either way, the new pond should be stocked gradually with your own fish to allow the biofilter to keep pace with the stocking rate, avoiding the lethal implications of New Pond Syndrome at all costs. 

An effective method of instantly seeding your new pond and filter with a diverse and healthy population of autotrophic and heterotrophic bacteria is to take media from your existing mature filter. This removes the need to wait until your filter is colonised naturally by successive bacterial populations.  


Having secured your koi a new home, (whether an obliging koi keeping friend, or a mature, temporary system), the koi should be floated on the pond’s surface for 5 minutes for the temperatures to become equalised. The bags are then opened, necks rolled down and system water added to mix water the qualities and temperatures further, ready for their koi to be released. If koi are being added to a new system from a half-way-house, then only a handful of fish should be added at a time, following the same acclimatisation procedure. 

Additional fish from your collection should only be added to your maturing temporary set-up once the water tests show that the filter is coping with the current levels of waste. The single most informative test is nitrite as this tends to be more persistent and more difficult for bacteria to breakdown than ammonia and once your filter can consistently produce a zero nitrite reading, then you can safely add more koi to your collection. 

Jumping Koi 

jumping koi Be sure to cover your temporary pond with a tight net as newly introduced koi do tend to jump during their first few days in a new pond. Check your koi closely on a regular basis for several weeks after the move so you can notice and treat any bumps or bruises that may have developed from the stress of the move. 

Watch out for individual fish that appear to sulk or lose their appetite as these are likely to be suffering individual problems. If your koi collection as a whole show similar behavioural signs then test your water and identify any factors that continue to stress your koi. Take a mucus sample and view under a microscope to assess the density of external parasites and treat accordingly.



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