Winterizing Your Garden Pond

Frozen garden pond Watching as winter transforms your garden pond from clear crystal waters and upright green luscious marginal plants to a white opaque frozen often snow covered expanse of water and brown frost tumbled plants can cause a little distress or even sadness in the heart of many a garden pond owner, especially if you have become more than a little attached to your pond and pond fish during the summer months, you may be forgiven for lamenting over the end of a great and productive summer season for both plants and pond fish, and reminiscing over, times spent relaxing by your pond, feeling the days stress just fade away, recalling balmy summer evenings with a cold beer or glass of wine in your hand, watching the goldfish play and the dragon flies swoop and dive between the water lilies, it all seems too distant a memory now winter is nearly here.

Pond Maintenance 1

Closing down your garden pond in preparation for the winter months that lie ahead is for certain a bittersweet time. You can ease the transition that has to take place at this time of year by looking forward to next year and another season of relaxation and rewards and ease the task of reopening your garden pond next spring a little for yourself and the pond, by following a few simple steps. of fall pond maintenance for your garden oasis.

Over Wintering of Pond fish

In late fall as temperatures start to get colder and colder you should start to feed your pond fish less and less as the pond water approaches 45deg c do not feed them at all. To help your pond fish successfully come through the hibernation period the winters frozen waters enforce upon them, in early fall you should make it part of your pond maintenance strategy to start to feed your pond fish a vitamin and mineral enriched fish food or supplement to their diet ,to help the immune system of your pond fish become stronger and resilient to infection a healthy balanced diet will also help your pond fish to produce the extra supplies of body fat necessary to sustain them through the winter hibernation period. During Fall months you should monitor the water temperature of your garden pond very closely if you don’t own a pond thermometer now is the time to acquire one When the pond water drops to around 55 deg only feed your pond fish when they are acting up at the top of the garden pond on the hunt for food . If they are hanging around at the lower levels or at the bottom of the pond do not feed them at all.

winter feeding of pond fish

Only feed your pond fish what they will readily consume in only a few minutes (10 or less) and remove as much of the uneaten food as you can, this is really a sound pond maintenance practice to follow at all times of year not just in the cooler pre-winter months when starting to think about pond closure.

Ammonia builds up is the number one fish killer at all times of year not just in the winter and excesses of uneaten fish food will only begin to decay producing the fish-killing ammonia. Ammonia is produced in several ways and is, in fact, part of the natural biological process, of pond life, known as the nitrogen cycle, when organic matter is introduced into the pond, by dead plant life, fish waste unconsumed fish food and pond fishes own gill function etc. ammonia is produced ,. .
Even on very warm fall days where the water daytime temperatures may rise above 45deg it is extremely ill-advised to feed your pond fish even if they seem a little action as chances are their metabolisms at this temperature a very sluggish the food will not be consumed and that at night time water temperatures will once again fall below 45 and the fish will be unable to metabolize the food.

Winter And The Garden Pond Nitrogen Cycle

Pond Maintenance 2

During the cold of the winter months the metabolic and circularity systems of the pond fish slows down, almost entirely but their respiratory system (their gill function) ie their breathing is still fully functional and despite that their metabolic functions have slowed right down they have not ceased completely and the pond fish still produce bodily waste and excrete it into the water. So the fish are trapped by the ice in a much smaller body of water than they are used to with a much greater concentration of ammonia this is why. It is very important to allow dissolved oxygen to pass into that remains unfrozen at the bottom of the garden pond. It is necessary to take some action to prevent the build-up of ammonia and carbon dioxide around the fish A deicer (heater) is just not enough sure it keeps a space on the surface of the garden pond free of ice formation but it does nothing to dissolved oxygen to the lower regions of the pond that the fish are actually inhabiting in for this an .Aerator/Circulator (air stone) does a better job as it constantly adds dissolved oxygen to the depths of the garden pond as it pumps the air right from the surface and with each little explosion of bubbles it releases dissolved oxygen to the the still liquid areas of pond water below the ice, while pond heater helps to keep a hole open in the surface of the ice and certainly does allow some of the toxic gases to escape from the garden pond the combination of air stone and heater do a much better job at protecting your garden pond fish through the winter Even if your winter temperature became too much for the pond heater to handle and the area around the unit froze completely the aerator in the bottom of the garden pond would still continue to work pumping a fresh supply of oxygen to the fish below the ice .

Over Wintering Tropical Pond Plants:

Tropical plants are not going to survive through the cold winter temperatures and should actually be removed from the pond as soon as water temperatures get to around 60 deg. Some Depending on the variety can be taken indoors and will, with good light, and enough water can be treated as houseplants. until you return them to the garden pond next spring.

Plants such as Water hyacinth and water lettuce take a lot of effort to keep alive as just houseplants all winter , but I have had considerably more success when overwintering these type of plants, allowing them to float freely as they regularly would in your garden pond but instead indoors on top of a largish fish tank over which a grow light is suspended the tank either houses indoor tropical fish or a few of your pond fish brought in to provide their body waste to implement the nitrogen cycle inside your tank. Bringing in pond fish over the winter seems a crazy practice when you purposely went to all the trouble in the first place to dig your garden pond deep enough to overwinter your fish outside.

spring algae bloom in the garden pond

Well if you only have a small stock of pond fish then yes it would be rather a silly idea ,but the longer you keep a garden pond for, the more fish you will obviously acquire, so to scoop out a few, allows you to decrease the amount of ammonia released in the bottom of your garden pond as you have diminished its population of pond fish which in turn lessens the amount of ammonia produced creating a less toxic environment for the remaining fish. Bringing a few pond fish indoors allows you to overwinter tropical floating plants which in turn ,allows you to get a head start , as soon as temperatures are right outdoors the following spring to add your overwintered floating plants back into your pond , those extra couples of weeks you get for yourself by not having to wait for new supplies of tropical floating pond plants to arrive at your local nursery allows you to provide earlier pond cover for garden pond and pond fish. This early start can often prevent that famous first bloom of green water from occurring in the spring.

The bacteria housed in your fish tank filter can be added to your pond biofilter to give it a kick-start for the new season no having to wait for it to kick in of its own accord. The fish you brought in is bigger and healthier than the ones kept outside as they have been constantly feeding and have not had to go into hibernation mode. Often I have found on releasing my captives back into their garden pond home they are now far bigger than their relatives who overwintered there. However I would like to point out that I originally started to bring in a few pond fish each winter, not for any of the mentioned advantages this practice provides, but because I missed being able to watch the goldfish’s antics throughout the winter months.

We had a huge 3x3x 6 tank that housed one lone Oscar occupant (now some oscars eat small goldfish, we knew ours was to fat and lazy to expend the energy involved in the chase so we knew we were safe to do this) The Oscar although he didn’t eat or harm the goldfish he did greatly enjoy bullying them when ever possible showing them just who was king of the tank ,that much so that when we put the goldfish back into our garden pond in the spring the Oscar (Rocky) appeared to become quite dejected and lonely, that much so that we went out and bought a plectomus (sucker fish) to add to the tank as his friend and Rocky was instantly happy again.

However most garden pond owners consider these types of tropical pond plants as annuals and treat them as such, they compost them and replace them each spring. Do not leave any of the tropical floater plants on the surface of your garden pond because once the freeze sets in, they will very quickly begin to decompose and contaminate your pond water. In the case of such tropical plants as elephant ears and canna lilies, you will need to remove and store their tubers, (clean and trim some of the root systems from the tubers remove all remaining foliage and store them in bags or trays filled with peat moss for the winter. Some of the more tender perennials such as the umbrella plant can be kept for the winter indoors .as houseplants if well-watered and fed occasionally.


  • Special Thanks to Ricardo Marquez for the lovely photo!