When should I turn off my bio filter for winter?

Natural Bio Filter

A  good rule of thumb is to run your bio filter whenever your weather is warm enough to grow and mow your grass.

The philosophy behind this rule of thumb is that the grass grows when the soil has warmed enough for bacteria to start the nitrogen cycle needed for its growth.  These are the same types of bacteria that are needed for your bio filter to function.  So, when its warm enough for soil bacteria, its probably warm enough for native beneficial bacteria in your bio filter. Conversely in the fall when it becomes too cool for the bacteria to operate the nitrogen cycle in the soil, it is probably too cool for the similar bacteria in the filter to function either.

  • For folks down south where your grass grows all year, run your bio filter all year.
  • For folks in the temperate regions, such as here in the Mid Atlantic, it is normally cold enough by Thanksgiving to no longer need to mow the lawn.  That is when to turn it off.  Our grass begins to grow again in April, so that is when we turn it back on.  Resist the temptation to turn it on with the first few warm days of spring as it almost always turns cold again, several times, before reliably warming up for the season.
  • Up north, you have a much shorter season, but let mowing be your guide.  Need to mow the emergent grass in spring, turn your filter on.  No longer need to mow your lawn in the fall, turn your filter off.