[IMG]file:///C:/Aquatics_WebSite_BU/articles/winterpond.jpg[/IMG]GETTING YOUR POND READY FOR WINTER
There is a little more to it than a last minute insertion of a heater to leave a hole opening for the gas to escape during the winter.
The first consideration is if the pond is suitable for over wintering fish ? If the water temperature drops too low the fish will not survive. The koi fish farms in Negata keep their less than one year old fish indoors the first winter The early Japanese farmers who raised magoi as a food supplement used to place logs over their ponds because of the heavy snow load and experienced heavy losses. Yet the magoi being the ancestors of koi were much stronger. A lot of koi keepers in northern New York State bring their koi indoors for the winter. One of course would have to make sure you have a well ventilated area as the humidity could prove harmful to a home. A heated garage would be better, good ventilation is still necessary as there is a danger of mould forming. Another problem is light you need the same brightness as growing lights. The Japanese still use greenhouses which are extremely expensive to heat. It is felt that a fine moss has to grow on the sides of the pond to have a healthy environment.
Let us look at what is required in over wintering koi in Ontario. The winter is a lot harsher if the frost comes before a snow fall it can penetrate several feet that is why a building code is 4ft deep for a ground frost wall. So gradually sloping sides are not only an invite for predators but they are no help in retaining heat as the shallower area does not retain heat and any surface area exposed to the elements. A shallow area can contribute to heat loss. Only the lower area of the pond that receives heat from the ground allowing the water to stay warm enough to keep fish alive. If the perimeter is protected on the outside by insulation it is a big plus.
Very often it is not the not the winter that kills fish. The problems can start in the autumn or spring. Amongst other things the fluctuating water temperatures can put fish through a lot of stress not a very good thing to happen for the long winter.
Koi are exothermic that means that their body temperatures match the water temperature they are in. When there is a sudden water temperature change in the fall from 25C in the day to 0 c at night. An unacceptable fluctuation occurs. Especially in the shallower small or sloping ponds. If you can foresee a cold snap turn off that waterfall and cover most of the pond with bubble wrap or sheets of foam to stop that wind chill on your pond. A better option at this time is make some sort of framework and use a 6mil plastic cover this is the most desirable method of protection for the winter. This again applies in the spring following this method you could even get an extra few weeks of feeding in.
You can gradually slow down your feeding. There is no need to change your food. You can greatly help digestion by pre-soaking before feeding. If you do changes for the winter feeding then it is possible that they might spit the new food out which is quite normal till they get used to it.
As the temperature gets colder there is no need for aeration of pond and filters as cold water holds more than double the amount of oxygen. The circulation could further cool your pond.
If you do not have a bottom drain the sludge from the bottom of the pond should be vacuumed out. As well as making sure that no leaves fall into the pond a skimmer or having a leaf net is a great help. Do not leave the cleaning till the last moment as the fish will be stressed and their immune system a lot lower. Again the people who put up a tent type structure over their pond have proved to be the most successful in keeping their fish alive.
For those who do not have a cover over the pond it will freeze is not a bad thing to happen. Ice on top of the pond will stop the wind chilling effect especially the snow which is a great insulator. A large covering of snow will block of light to the pond which can result in the fine moss on the pond walls to die causing a build up of more gasses. So it is wise to scrape a section clear of snow however do not trample it all down around the pond as snow is a great insulator. Sometimes you can be lucky and get snow before the frost has penetrated to deep. You still need an opening in the ice for ventilation of gases. The lowest cost is one of those small heaters which draw 100w and leaves a small centre hole open You do not need a great big hole so you could use a small ornamental water pump below the surface will do the job. Air stones you should be careful with unless the unit is located inside the house you are going to be chilling the water over the winter you could drop your temperature by 2c and this could prove fatal to your fish. A bubbler can easily open up a large hole and the night can result in sudden chilling. Gas bubbles are bad news and that includes air. You can actually get supper saturation. If using a bubbler put a stick in the open water and if you see a lot of bubbles on it you are approaching the dangerous level. Koi develop a pop eye condition in supersaturated water condition. So if you notice either of these conditions disconnect the air.
One of the myths of cold water fish keeping is that once the temperature drops below 10c fish such as koi cannot digest food. Recent research has shown that koi eat and digest food between 3c and 10c but very little and usually natural foods such as algae.
At 3c most filtration systems cease completely yet ammonia is produced even if it is in small quantity. Ammonia does not go away in fact it builds up over the winter as well as decomposing leaves. So do take a reading during the winter make sure that you warm the water to requested temperature and your kit is not outdated or has been exposed to temperature extremes . Remember that if you get any ammonia reading at all it is generally a 100 times too high as it is impossible to show minute quantity on low cost kits. You should take a sample from near the bottom of the pond. Putting a pump in and circulating the water does not really reduce water contamination it just stirs it up.
Because of our long winter it is a good idea to do a partial water change during a mild spell. One has to be careful not to suddenly increase the water temperature by more than 2c at a time. Our Canadian winters are just to long to wait till spring.
Spring is the most dangerous time of the year. Koi are in a weakened condition and are looking for food. The bacteria in the filter units has not matured and may not do so for 6 weeks. You should treat your filter the same as a new pond and check for ammonia daily. It is a big help if you add bacteria from an established pond or a safer method is to purchase some pond start.
If the temperature is not high enough will take a longer time to get bacteria established and if it is taking too long heating the pond is a good method certainly covering for the night would be highly beneficial.
In the spring the immune system being at its lowest in fact it hardly functions until the water temperature is over 12 c. On the other hand parasites can flourish at low temperatures and any injury can quickly be attacked by aeromonas bacteria which can develop into fatal holes in the side. An excellent remedy is salt as a spring treatment as it will kill most parasites. As well as spending a little money on heat especially if it is a long cold spring.
If one of your fish has problems it should be caught and put in a quarantine tank, gradually raising the temperature so its immune system gets increased. One has to be cautious not to disturb the other fish and stress them. You will have to take skin scrapes and identify the problem before considering any treatment.
Fish sickness occurs because of poor water quality in most cases hence it is often said that we are water keepers. Treatment by chemicals further pollutes the water certainly most treatments are harmful to the filtration media and require oxygen.
The only safe treatment is salt and will work in most instances. It can be added to a level of 3lb per hundred gallon gradually and then reduced with water changes. If you have used salt in the fall then make sure you do not have a level of more than 1lb per 100 gal for the winter. You can use strong solutions and 10 min dips but I consider them drastic measures nearly as bad as the brand name Chemical treatments.
Water changes is your best way of getting rid of sudden spikes of ammonia readings. As well you should stop feeding immediately. Again everything has to be done slowly or in moderation as excessive water changes can cause a slowing down of your bio filter as you could be removing a lot of beneficial nitrifying bacteria.
Feeding in the spring is very much like the fall. You should throw away all opened food as it will have little nutritional value and it might even be stale. Again soak the food as this helps digestion so it does not just pass through the koi creating extra ammonia which the bio filters can not handle.
CONCLUSION
My over wintering pond has proven quite successful, even when outside temperatures dropped to -30F over night, the pond water temperature still stayed at 42F. This temperature was not just achieved by the greenhouse lean-to structure covering the pond, the pond itself was covered in the evening with a swimming pool bubble wrap cover.
Another contributing factor is the steady trickle of water flowing in, about 3000 gallons a week. The water flowing in (directly from the well) is 48F, the supply line snakes its way through a coil above a heated area atop the waterfall, and out a soaker hose and is allowed to trickle down the front of the waterfall. This raises the incoming water temperature to 51F.
In my over wintering pond, where the steady trickle of water enters, all the koi gather, near the warmer water. The male fish as well as most of the females, seem quite happy with the exception of one older female and a 3 year old from Japan, they have their fins clamped against their body. I am sure that a few days of 42F will not will not do them any harm, and with a couple of sunny days the temperature raises to 48F. I do have the option to heat this pond if I need to.
An over wintering pond is certainly better for the health of the fish when outdoors, everything is completely frozen over where water temperatures drop to 37F when koi even lay on their sides. It is generally agreed that colder temperatures can kill larger females and prolonged winters can shorten life spans. A winter dormancy period of 2 months and a water temperature of 16F is recommended .
So best of luck this coming winter.
Eugene Gmitrowicz
01-04-2008
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