Figure 1: The red in this pond is actually an algae species call Euglena. (photo: Science Source)

The Frog Blog

This is probably one of the most common questions someone may have as they look at their pond. It can also be a difficult one to answer as well considering not all green-looking things in a pond are algae and not all algae is green (Figure 1). So how does one distinguish nuisance algae growing in their pond from something else? Having an expert such as an AQUA DOC specialist visit is one very easy way to identify what’s in your pond but it can also be fun to try and do it yourself! Here are some tips to help guide you as you look at your pond:

  • Note plenty of observations. What color is it? Is the growth on the surface or seem to be within the water column? How does it feel when you squish it in your hands (always wear gloves!)? Does it separate from itself when you break the water surface tension?
  • Use pictures and guides. Smartphones are great to easily research photos and apps exist that can aid you in the process. is a great resource to look into!
  • Get multiple opinions. People can perceive things differently and having someone with you while you’re observing you’re pond could open up a different way of looking at what’s in it.
  • If you get stumped remember that there are specialists who are knowledgeable and happy to help and educate you about your pond.

Figure 2: Note the “milky” appearance of the pond. This is not from an algae source.

So, what is out there that can look like nuisance algae but actually isn’t?  A lot as it turns out. Warm summers are great for decomposition processes in ponds however, it can also result in an almost milky-looking film at the surface when organic materials become buoyant (Figure 2). In the spring and fall, various plants will produce pollen as a part of their natural life-cycle. Pollen can remain buoyant when it lands on water and be easily mistaken for an algae bloom. Other organic debris from outside the pond can also contribute to films if they don’t break the water’s surface tension. These are just a few examples of common non-algae films that can be misidentified.

Figuring out exactly what is growing in your pond is not always an easy process. Many differences between algae species require specialized equipment to allow us to peer into what can’t been seen by the naked eye.  Don’t be discouraged! With practice and research, you can identify anything growing in your pond.

By: Edward Kwietniewski

Aquatic Biologist

AQUA DOC Lake & Pond Management

Edward Kwietniewski graduated from The State University of New York College of Environmental Science and Forestry (SUNY ESF) with a Bachelor’s degree in Aquatics and Fisheries Science. He also has a Master’s degree in Lake Management from the State University of New York College at Oneonta (SUNY Oneonta). He has a love for all things aquatic and is an avid fisherman.