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How does winter affect my pond? – Ponds & Lakes Q & A

Winter PondQ:  How does winter affect my pond? – Steve in Michigan

A:  A Closer Look at Water in the Winter…

We field many questions about water and the way it works during the winter.  With such a range of questions, here is a quick course on the physical properties of water and how they relate to your pond.

Here’s a review on density.  On our planet, matter that is denser will always be pulled down (gravity) more strongly than matter of lesser density.  Density is temperature dependant in that warmer matter is always less dense than cooler matter.  A good example is a hot air balloon, which lifts up because the air inside the balloon is warmer than the air outside.

A water molecule (H20 – don’t worry that’s as technical as we’ll get) contracts as it gets colder, causing it to become more dense.  As water closes in on the freezing point, we run into one of nature’s great exceptions.  At 39ºF (4ºC) water actually starts becoming less dense as it prepares to shift from a liquid to a solid at the 32ºF mark.  Why is this so important?  This means that water at the bottom of your pond will always stay about 39ºF because it is the heaviest.  We refer to this as inverse stratification, where a pond has a thermocline that separates warmer water on the bottom from cooler water on top (FYI, normal stratification occurs during the warmer months of the year when the cooler water is at the bottom and the warmer water is at the top).

Winter PondHow does this apply to your fish?  Fish actually get quite sensitive to temperatures below 39ºF.  This warmer 39ºF pocket on the bottom of the pond is where they tend to hang out during the winter.  This is why it is recommended that an aeration system be installed a couple feet up from the bottom of the pond to keep the 39ºF water in tact. Should you worry if yours isn’t? No, not really, mortality due to water temperature is extremely rare and NOT aerating is way more risky. The more severe issue is the toxic gases under the ice. Continuing to aerate will vent these gasses while also infusing oxygen into the water keep your fish happy and healthy.

How do I know when I can feed my koi again? – Decorative Ponds & Water Gardens Q & A

Koi FeedingQ: How do I know when I can feed my koi again? – Jim in Michigan

A: Now that we’re at winter’s peak, many of us begin to think about the coming spring.  As we start the spring to-do list, we remember those poor little koi that are out in the water garden.  Since you’ve kept a hole open in the ice all winter, you really have nothing to worry about, right? But your koi seem to be a little more active lately with the approaching spring and look like they have a mighty appetite since they haven’t eaten all winter. Should you start feeding now, or later? This all comes down to water temperature. Let me explain.

During the winter months koi go into a state of near-hibernation where their bodily systems are doing just enough to keep them alive.  Much like the frogs and turtles, koi typically do not eat during this time.  This is because their digestive tracts have slowed down so much that food cannot be fully digested by their stomachs. It is for this reason that we recommend that you stop feeding your koi altogether once water temperatures dip down below 40ºF.  As water temperatures being to climb between 40ºF & 55ºF the optimum food to feed your koi is a wheat germ based fish food like Spring & Fall Fish Food.  Wheat germ is specifically designed to be easy on the digestive tract for koi as they transition in and out of winter.

Fish FoodSo in summary, during the spring thaw watch your water temperatures. As they approach 40ºF, you will notice the koi becoming more active. At this point, throw in a very small amount of Spring & Fall Fish Food to see if they are interested. Once they start eating the pellets, you can begin ramping up the spring feeding. As the koi eat, continue to increase their rations (never more than they can clean up in a few minutes) until the water temperatures reach their normal levels for the summer. At this point, switch them over to a higher protein fish food like Growth & Color or Professional Fish Food.

POND TALK: When do you start feeding your fish?


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