Why is My Pond Green?

Typically, no one really wants a green pond.  Sometimes what’s causing that green color may be harmful to your fish and pets.  Other times, it isn’t necessarily harmful though it’s just not aesthetically pleasing and can impact your ability to use your pond whether it is for swimming, fishing, water supply or just decoration.

The First Questions to Ask

So, why is your pond green?  The green color in a pond could be the sign of several different issues.  The first step is figuring out specifically which problem you have, and then treating that issue.  Before you try to tackle the problem, ask yourself these two questions.

  • Does the pond look green throughout the water column, or just on the surface?
  • Do the green areas cover the whole water body uniformly, or is it patchy?

Algae, Floating, and Submersed Weeds

If you answered “just on the surface” and “patchy,” then you’re likely dealing with some form of algae.  Algae are often referred to as moss or pond scum. They are photosynthetic organisms that can grow in mats or scums that cover the surface of the water.  They don’t have true roots or leaves like most aquatic plants, and they feed on excess nutrients like phosphorus that can make their way into your pond from runoff, fish food, geese or a number of other sources.

If you answered “throughout the water” and “uniformly distributed,” then you’re probably dealing with floating weeds.  Floating weeds are just what they sound like: weeds that float on the surface of the pond, some may grow up to the surface though are attached to the floor of the pond.  However, there are floating weeds that grow completely unattached, so don’t mistake these for algae.  Watermeal and duckweed are two very common types of floating weeds and are both difficult to control.  They look like very tiny leaves or round balls covering the surface of a pond.

Additional potential culprits are submersed weeds.  These are weeds that grow entirely under the surface of the water and are attached to the floor of the pond.  These plants may give the illusion of green water simply because of their location in the water.

Identification and Treatment

Now that you’ve answered the question of why your pond is green, you can consider a treatment. Before planning a treatment, it’s necessary to know and understand what’s growing in your pond. Otherwise, you will find yourself spending money on a treatment that may not be suited for the issue in your pond. The easiest way to know for sure is to have your pond tested. A sample can tell a professional specifically what’s growing in your pond, and that person will be able to make an informed recommendation about a product that can take care of your problem and get your water clear again.