Pond algae in the winter? You’ve got to be kidding right?
For those that keep their ponds open all year round, and particularly for people who live in colder climates, it can come as a shock that they would actually have pond algae growing in the water or on the rocks, even when it’s cold outside.
Keep in mind that algae is one toughy of a plant at times. You don’t live for a bagazillion years and not have some adaptability. And while it’s true that most ponds will have algae issues as the weather warms up, some can still get a bloom in the winter. Some of this depends on the algae type as well as some of the elements in the pond water, as well as available sunlight. With regard to the latter, one might even see algae growing under ice as springtime approaches.
Generally winter algae isn’t all bad. Like any growth you ideally don’t want it to overwhelm the pond but fish my dine on it from time to time and fortunately the oxygen holding capacity of water is much better in cooler temperatures so as long as there is a bit of air exchange at the surface (meaning a bit of open water) then all should be fine.
For small ponds with a bit of string algae, it’s easy enough to physically remove some of the growth with something like the Algae Witch or similar device. You could also treat it physically with a product like Algae Off, which uses a peroxide based formula to kill algae on contact. I tend to prefer physical removal if it’s possible to do it.
So how does a pond stay in pretty good shape all summer and then get algae when it’s cold? In regards to smaller ponds, many of these will still get a build up of some organic debris over time and while this decomposition slows a great deal it can still affect nutrients in the water. One might get a little bit of fish waste too from time to time. Along with this, most biological filters are turned off when the temperature get’s below 45 to 50 degrees. With this function disabled, the normal cleaning and balancing processes that would be in place during warm weather are no longer available. And finally, many desirable plants that would grow well and outcompete algae in the summer are no longer present, and this gives algae a bit of a chance to get going.
Keeping the pond as clean as possible going into the fall and early winter may help a bit. Along with this it’s not a bad idea to try a cold water bacteria blend, which can help on any nutrients that may be present in the pond water. Although these bacteria will work well in water temperatures down to anywhere from 36 to 40 degrees, if the water get’s much colder they will probably go inactive for awhile.
The good news is, as the weather begins to warm up, fresh bacteria may begin to work well again, and once the pond filtration is activated again, the balance will gradually be restored to the pond.
Winter pond algae may at first come as quite a shock and may seem to be abnormal however it’s not unheard of by any means and there are ways to deal with safely and effectively.