Q: That isn’t algae growing under the ice, is it?
A: A common question that we receive in the winter pertains to winter algae and what to do with it. In the northern climates, there are strains of algae that do thrive in temperatures down to freezing. The good news is that typically these strains do not reach nuisance levels in ponds or lakes. They tend to hang out in warmer locations, usually around an inflow of water, where it is nice and sunny. In optimal growing conditions, these algae can generate enough biomass to put your fish at risk. A sudden die-off caused by a sudden swing in temperature, overcast weather, etc. can deplete the dissolved oxygen levels under the ice which leads to unnecessary fish stress.
Solutions: Nutrient management in your watershed as well as your pond will slow down the growth of any algae or plant all season. Typically phosphorus is the key nutrient for algal growth, so try switching to phosphorus free fertilizers if you fertilize your lawn. Our Pond-Clear Packets and Pond-Clear Pellets eat away at the muck/nutrients found in the pond. Our Nutri-Defense Packets bind up any excess nutrients flowing in from the watershed. These are things to do in the summer, but what about winter? With the pond frozen over, your options are limited. Dying the pond a deep blue with pond dye will reduce the amount of sunlight that passes through the water column. If you can safely do it, I would suggest adding an extra dose through the ice to slow down growth.