Why is my pond water sooo clear when it starts getting cold out?
I hear this question every year as the temperatures being to fall and the pond season in the northeast starts to come to an end. It is a good question too. Any one who watches their water quality probably cannot help but notice that pond water, during November and just before ice covers the pond’s surface, gets super clear. A great part of my job no matter what time of year is to make sure that my customers’ ponds have clear water. If it is not clear I have to know why and then remedy it. With experience it can become pretty easy to figure out why a pond is not clear, and take the corrective actions to get that water clear again.
Everybody loves when their pond water is clear. Clear water just makes enjoying the pond so much easier. Everyone loves to see all their fish and plants, and have clarity to the bottom of the pond. This has become an expectation with most pond owners these days. I am pretty fortunate to be able to diagnose water quality issues and clarity issues effectively, and provide the solutions to get the water back to its’ clear beauty.
When the cold season comes though, the water clarity is at it’s finest in most ponds that I deal with. In my pond too, it is just a delight to go out especially at night when the pond lighting is on and see that “crystal” clear water condition as if there was no water in the pond at all. If I could get this type of clarity during the height of the season I’d be thrilled.
So why is it that pond water is clearer during this time of year? Well, the answer really is pretty basic. Nothing magic is going on, I am not using any special treatment or clarifier to achieve this level of water clarity is simply because…..
Well, before we get to the answer, let’s look at what reduces clarity in our ponds first. When we fill our ponds the water going into the pond is completely clear. So what is making our clear water have reduced clarity? Several things are to blame, and it is simple pond math, so let’s add them up.
Our pond water (and drinking water) has tiny little floating pieces of algae that are mixed throughout the water column. These little planktonic algae cells produce chlorophyll, which in turns reduces clarity. In extreme circumstances the chlorophyll production will actually make our water appear completely green, yes, the condition we in the industry call “green water”. Even just a small amount of color production in these algae cells will play a role in hazy water and reduced clarity.
There is no question that aquatic plants play a large role in water clarity; but at the same time all the plants that we have in our ponds are constantly sloughing off bits of themselves that then float around in the water until they are filtered out. The dirt that these plants are growing in is kicking up little particles as well, adding to reduced clarity.
Food!! We love feeding our fish. The food we are putting into the water for our fish breaks up and dissolves into particles that also float around until filtered out; of course the food that makes it into the mouths of our fish will only be there temporarily until it inevitably passes out of the other end of our fish as fish waste (poop). Fish poop does what? It breaks up into particulate matter that filters or settles out of the water column, but before that happens it is happily floating around reducing our water’s clarity.
Once all these different particles of different materials settle down to the bottom of the pond we should be able to forget about them, but if they do not get filtered out by pond gravel they are very likely to be swept back up into the water column again by every swoosh of our fishes tails and fins, to then float again, reducing clarity. So, even the simple action of the swish of a fin will reduce clarity!
When all of these particles from all these different sources are added together and floating around in our ponds, the “math” says it is a wonder we can see anything at all! This is one of the many reasons why good filtration is important for your pond. So here comes winter, the great subtractor of pond particles.
The winter months will allow us to take away daylight hours. Less daylight is less algae cell production and chlorophyll production, and that gives greater clarity. The lower water temperatures in the water slows down the plant growth, so we now have less plant particles in the water and that too gives us better clarity to the water. Our fish do not want to eat as much with lower water temperatures, so we stop feeding and that eliminates food particles, less food intake results in less fish activity and less fish poop, so our fish are not swimming and kicking up particles from the pond bottom or pooping as much; and this all gives us better clarity.
So, subtract all those factors and it is easy to see why our water clarity improves during the winter months, but wait! Add to that equation the fact that our filter system that keeps our ponds clear even at the height of the season is still running at full capacity. The filter is now eliminating all the left over traces of particles that were happily frolicking in our ponds water column. So what do we get? We get some really REALLY clear water conditions. You see, it is just simple pond mathematics.
Here is your caveat though. Enjoy these clear water conditions while they last because soon enough winter will really kick in and freeze over the pond with ice and snow, hiding away that clear water that we strive to enjoy so much until Spring comes again. Enjoy it for what it is and enjoy it while it lasts!
All copyrights to this material belong to Mike Gannon.



Mine is opposite, I always have to seem clean clear water and minimal algae in the summer, come winter, i shut the system down, algae takes over, the bottom is totally covered with this green monster. Water is clear, but no more clear then in the summer. I do feed my fish once every two weeks, but then again, i have a small filter connected to my small aeration pump, and I’m sure it can handle a sprinkle of food twice a month. My winter water is completely opposite =)


These type of water conditions seem to be isolated to the areas where the weather turns very cold. A great deal of the clarity is due simply to the inactivity that the lower temperatures bring on. Thank you for the comment.

Rebecca Cooper

So, are we never going to have clear water and be able to see our fish is the summer? What do we do?

Rebecca Cooper

So, are we never going to have clear water and be able to see our fish in the summer? What do we do?


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