It is getting close to the end of active koi keeping season for many of us now. And preparations should begin in the next few weeks.
If you are in the east coast region of the USA from DC up to upstate New York ( this also holds true for England I’m sure) you will notice that your koi’s appetite is beginning to change.
Because your koi is truly part of its environment, changes are happening IN the koi and AROUND the koi at this very moment.
Your koi’s biological clock, triggered by night time water temperature, air surface temperatures and light changes, now is telling the koi what is about to happen- winter! This clock is also telling the females that spring breeding isn’t so far off and preparations must be made for that event as well. Therefore you koi will get hungrier! You will notice that they will eat more aggressively. Part of this is due to higher oxygen levels and better OPR readings this time of year which results in better water quality in general and part is the considerable influence of that biological clock.
You must now decide what you will be going with your fish come Dec. 1? Will they be under a protective tent or inside? Will they be left under ice to take their chances or will they be given only the illusion of winter ( mild heat and covered)? Only love, depth of concern, monetary value and economics will determine this answer.
In the ideal, your pond should already be netted ( berry netting available at any garden center or Home depot) to keep falling leaves, twigs and airborne materials from settling into the pond. The koi should be moved to a wheatgerm and fresh food diet about now and away from the high protein pellets. The number of meals and amounts can also begin to come down. I feed the same number of times this time of year ( three or four) but I reduce the amounts and already have opened my first bag of wheatgerm pellets. As water cools and the sumps are less burdened by organics, you will notice your koi’s white skin get much whiter.
Once Nov. Rolls around, your tent should be completely installed and ready to go as the cooler nights of late November will bring the water temps down considerably. During this time, you can usually depend on solar effects during the day and you can close the tenet at night to retain some heat. Remember, the tent acts as a heat space that separates your ponds water surface from the cooler air. My heaters usually start going on and off during the week of Thanksgiving. Once you water hits 50 F stop feeding. If you must, for emotional reasons, feed the koi- feed very small amounts and fresh food is better than pellets.
Now you are in the ‘ winter zone’. This can be real or man made. The difference being -a conscience decision to:
A) flirt with the carp population’s known survival ranges or
B) to limit the ‘ winter zone’ to individual koi’s optimal temperature range.
This is simply saying that at the most basic and primitive koi keeping level, temperatures near or below 0 C ( 32 F ) will test the survival abilities of each koi- young/old, well conditioned/ poorly conditioned. And nature tells us that a large percentage will make it through the challenge with only minor health issues the following spring. This older technique is pretty much passe in modern koi keeping but some water garden hybrid koi keeper types still practice it to this very day. And even this group is divided into those that let ice form and those that keep the ice off and keep things running. Both have their gamble. One allows gas to build and if a koi dies, that death can stress, sicken or kill the other fish. The no ice crowd will keep koi swimming in cold water and if the winter is long, the koi run out of gas and stress, sicken or die. This also allows winter precipitation to influence water parameters and water quality. And allows water to actually drop below freezing at some point- negating the passive warming effects of the earth. So IMHO the pond MUST be tented .
The second, more evolved approach B ( heat and tent) is to only allow temperatures to fall low enough to give the effects of the ‘ winter zone’ without testing survivability of each individual fish. This gives the desired effect in regards to the fish’s metabolic needs and seasonal shift but not an exhaustion or associated stress of a full blown winter survival challenge. This low end range then would be 45- 55 F/ 8-13 C.
The next decision that will separate ‘survival’ from ‘optimal’ will be the length of the ‘ winter zone’. The winters in the North East are long! As they are in England. In the primitive technique of koi keeping, a young koi may be asked to hang on for as long as 16 weeks. This is a lot to ask of the better breed koi from Japan. So parasites in spring, the illusion of a thing called aeromonas alley and general infection are all very real possibilities. The koi is simply weak and exhausted. An easy target for a pond that is becoming biologically active in an organically rich warming environment.
In the second technique, a man made artificial ‘ winter zone’, the winter cycle can be easily controlled. ‘winter’ can be as short as 6- 8 weeks and never dip below 45F. But be aware, low light conditions will still keep koi inactive and experiencing the seasonal influences.

* Regardless of which path you take, the pond should be kept clean and netted as the winter zone approaches. And normal maintenance should continue, albeit reduced somewhat. Water changes should continue, only smaller and less often. Sumps should be dumped, only less often.
* Equipment should also be checked as we all tend to not want to go out there! I also recommend a spare pump in reserve for that Sunday morning disaster!
* Drain all ‘ summer lines’ that can freeze. Make Thanksgiving weekend your drop dead date! If your are going to go ‘ primitive’ you need to consider freezing of lines- even if you keep the water running. This is why two speed pumps make some sense on one level and not much sense on another. Same is true with the use of ball values. Reduced flow with create a chance for ice to form and actually crack a schedule 80 ball value!
* stop all feeding once you reach your chosen ‘ winter zone’ . Another last minute meal is meaningless and can actually do more harm than good.
* the berry netting will keep ‘most’ leaves out but some how some will make it in so before adding the tent, make sure the bottom is clean.
* Look into buying a heater. This is the ultimate control over winter and the associated problems of the old way of keeping koi at the most primitive level.

I would like to thank JR for giving permission to post his thoughts here on Backyard Puddle. ~Terri

Temperatures begin to drop here in the Tri-Sate area!
As every koi keeper comes to learn , it is the nights and not the days ( lighting yes, temperatures, no) that begins the winter season for koi. Progressively, each night pulls the water temperatures slightly lower. Here in NJ, we tend to get into frosting night temperatures this time of month and on into the second week of December. Still, the mildest part of winter is with us.
Having kept records of winter water and air temperatures for my pond since 1985 I can tell you that each winter is different in some way, but all tend to follow a trend line if you look at the numbers on a weekly basis vs. a daily one. ( and at least ‘here in NJ’ global warming is hogwash LOLs)
It is also very common in my area to see a 'breakout' in trend such as a warming spell some years and a deep freeze some years. These ten day departures from the norm can come at any time but are most common in the months of December and February.

Something to remember for the beginner keeper-- the two biggest dangers your outdoor koi faces thru winter are ;

1) the length of winter--- some years winter lasts a full 18 weeks . These long winters are hard on koi as young, weak and old koi just can't store enough energy or can't tolerate cold water stress that long a period of time.

2) high fluctuation of temperature and pH in winter- ponds that freeze early then thaw and then repeat the cycle over and over are death traps for young koi especially. Ponds that receive a large amount of snow or sleet that melts into the pond also tend to swing in pH reading. This is highly stressful for the koi in stasis.

You MUST make a decision between several potential winter environments for your koi BEFORE winter sets in;

1) au naturale- letting the pond freeze and close down the filters for the winter was once the only way koi were kept. And then the WORST way to keep koi. And now brought back for economic reasons as the most practical way to keep koi. Ironically those that keep water moving and filters running can often benefit from an frozen surface as a protective barrier from wind, rain and snow ( all negatives for survival chances). But moving water needs to get very very cold to freeze! This is a case of a good intention ( keeping things running) delivering very bad, very cold results!! So if you keep things running, which is a good thing ‘on paper’, you need to take a second step and that is to cover the pond. A cover serves two purposes- a) it becomes the ‘ice cover’ protecting the water integrity itself and b) it does NOT lay ON the water skin. Instead it acts as a trapping air space to protect the water itself from wind chill and heat lose.
2) the luxury addition- the top flight way to keep you koi is to keep the pond running and ‘alive’ and also to cover and maybe heat the water. In this approach your koi’s survival is assured and the stress is minimal as the fish ‘slow down’ but are never running out of stored energy or facing Cold water stress ( a real killer as spring comes around). This can be a challenge for keepers however as it requires a designed cover that works, and some expense to heat ( solar and other creative options might help somewhat here. I’ve seen some VERY clever answers to this challenge over the last twenty years. One of the clever ideas I saw was having a green house that grew tomatoes act as a source of heat for the pond. Another was hooking a third zone off the house furnace and diverting that heat to the pond via a stainless steel heat exchanger. My own heating system is a series of heating coils placed inside the eight foot heating towers I use as Trickle towers. Many ways to go here.

3) the third, which might at first seem extreme but is actually the most practical is have a second, indoor system for winter. The indoor system must be large but does not need to be as ‘full blown’ as the outdoor show system. Good basic filtration which can house the outdoor media ( nothing like a biofilm that has survived the years!) Is good and fish should not be crowded but they can be stocked higher than is normally advised as these fish will eat very little during their artificial winter. You want the indoor temperatures relatively low and NOT like the summer temperatures. Anywhere from the high 40s to the mid 50s is fine. At 60 F you will need to have a bigger system, do more water changes and feed a little ( maybe twice weekly with a fasting period in Jan- Feb that lasts 4 - 6 weeks.

Something everyone must understand- you will get advise from the garden center and landscaping world that suggests you should keep koi in winter like plants. To the water garden mentality, koi are generic, without feeling or physiology and just hibernate under ice. This is an incorrect model of what a koi is.
If we do subscribe to the water garden/landscaper vernacular then I’ll introduce another concept here- ‘annual’ . This gardening terms means that something is born in spring, grows and then dies after the first frost. In the case of koi, young fry can be looked at as ‘annuals’ and replaced/ replanted next spring but that certainly does not need to be the case.
This is an excellent time to join an AKCA/ZNA club as you can pick up a lot of practical hints on keeping koi in your particular area. Each area is somewhat unique- but the koi are all the same in their basic needs. More specifically, there are true advanced experienced experts in every area of the country that understand those basic needs koi have and you have a great opportunity to learn the problems unique to your area ( not even the greatest Japanese breeder can help you with those unique challenges ). So join a club today.