Pond Turnover

What is a pond turnover?

“Pond turnover is a term used to describe the mixing of the stagnant, or ‘stratified,’ waters in a pond.  Stratification is an occurrence whereby the water separates into three distinct layers-like a layer cake-each with its own different temperature and dissolved oxygen levels” (Brandon Galbreath- O’Leary).

Most fish like to stay in water that is warmer because it has a high dissolved oxygen content. Warm water is in the upper layer (or epilimnion) of the pond or lake. The middle layer is called thermocline. It’s a transitional layer where the oxygen begins to lessen as it gets deeper into the lower level.

The lower level is called the hypolimnion. The hypolimnion layer is the coldest part of the lake and has the lowest amount of oxygen. You won’t find too many fish in the lower level of the pond or lake.

What happens during a pond or lake turnover?

The hypolimnion (or lowest) level becomes stagnant because it doesn’t touch the air. (That’s important because the air is what cleanses water). So when the warmer epilimnion layer starts to cool off like the lower layer, they mix which is called a turnover.

This typically isn’t a problem except when the hypolimnion level becomes so stagnant that it contaminates the warmer water above.

How do I stop a turnover?

One way is through bottom aeration. Bottom aeration uses air bubbles to create lift to remove the thermocline from your pond by keeping the water mixed up.

The dirty little secret that no one will tell you is that floating fountains, unless they have draft tube, will circulate only the water on the top three feet of the pond.  Why is this important?  Because this top three feet already has high oxygen levels and does not mix up the water from the bottom of the pond or lake.

Still interested?  Check out this Blog post about Floating Fountains vs Aeration

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