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Carbon, and Why It’s Important in Your Pond Fish health

by Joe Cadieux on December 29, 2022

Hello Friends……

There are a multitude of factors (environmental, chemical, physical, biological, whimsical and ethereal), that contribute to the conditions that you observe at any given time down at the pond.  Surface water, whether it’s a 2 acre pond or a backyard koi pond, has the potential to present you with an assortment of faces over the course of the season (or from year to year for that matter).  I have put together this article to shed some light on the basics of the elements that drive change in your pond.  There are bunch more factors that contribute to the conditions we see, but here I am focusing on carbon.

(I will be posting articles about nitrogen, phosphorus, and other contributing factors in the near future, so please check back regularly.)

Carbon (C):


Carbon carbon carbon carbon carbon chameleon ….. heh heh… yeah… (What….not big Culture Club fans? Well….. carrying on then)

I have absconded the pictures from the web to illustrate the role that carbon (C) holds in our waters.  Please notice the equation for photosynthesis from your eighth grade science class. This pile of letters is responsible for life on Earth as we know it…and drives water quality more than most people think. Looking at this equation, you’ll see the C that is the reason we, the people of Earth, can walk around and worry about pond health and maintenance. If we are able to utilize carbon in the aquatic environment more efficiently, it will lead to a more stable, healthy water column.

I am focused on the bottom of the picture from above.  The part with water (cuz I’m a freshwater biologist, for realz) is where the carbon cycle is most applicable to you and your pond.

Carbon accumulates in critters and plant biomass and is recycled through the resource (the water) through decay.  Decomposing plant and animal material that settles to the bottom of the pond is the main source of nutrients that most ponds have to deal with on a continual basis. The vast majority of this detritus is made up of organic, carbon-containing compounds. These compounds will be used by the resource. It is up to you to push the ecosystem away from using those organic compounds for primary production (plants and algae) and towards the creatures (fish, insects, bacteria) of the pond biome.  The more efficient you make your pond; the better the carbon cycle operates and the better your pond will look and smell.

The best/easiest/most efficient way to nudge this cycle along is through propping up the very bottom of the food chain.  The bacteria that is involved in the breakdown of the organic material that collects at the bottom of every pond (no matter its size) is aerobic in nature and will ALWAYS do better under high oxygen conditions.  For you that means: AERATE YOUR POND.  For smaller ponds, run the filter/waterfall as much as you can.  Oxygen depletes at the sediment layer very quickly (a matter of minutes). This depletion starves out the bacteria, limiting their growth and reproduction.  Get air down there!

The carbon that is present in the molecules abundant in decomposing organic material will re-suspend into the water column in one of four ways: (1) as parts of an aquatic plant, (2) as parts of algae, (3) as fuel for critters, or (4) as carbon dioxide (CO2) and methane (CH4) blowing away on the wind. My preferences are (3) and (4).  This brings us back to bacteria.  Bacteria gets eaten by larger organisms and zooplankton (which also do better in high oxygen environments…hint hint), and these in turn are consumed by insects and fish which are continually accumulating and concentrating all this carbon (among other important nutrients).  When the carbon is stored in fish and insects, it can be removed or cycled back through the system as the big wheel of nature spins around.

The end goal is this: store as much carbon out of solution as you can to make your pond a happy, healthy place.

  • Maintain a stable fishery to balance out the Carbon. (Harvesting fish is OK. I promise. Please see my article about fish health.)
  • Harvest off plant biomass in the fall.  Removing dead or dying leaves from water lilies and other aquatic plants eliminates a bunch of carbon from the system.
  • Bolster your bacteria with beneficial bacteria products and enzymes to make them even more efficient and abundant.
  • For watergardens: clean out the pond every year (or every other year) to keep the organics down.

I thank you very much for reading my posts, and as always, please ask questions or request topics in the comment section.


Senior Biologist



https://poseidonaquaticdesigns.com/ | https://girlsfromthegreenstuff.blog/ | http://bio1152.nicerweb.com/Locked/media/ch55/carbon_cycle.html |