Q: How would I know if my pond has sufficient aeration? What would happen if my pond was “under” aerated?
– Joe of Michigan
A: The best way to test to see if your pond is sufficiently aerated is by taking the temperature of the water one foot below the pond’s surface as well as the bottom. If there is a difference of more than 3 degrees Fahrenheit, then the pond is not sufficiently aerated and you may need to add additional diffusers or relocate the diffuser that you have.
Next, to answer the, “What would happen if my pond was “under” aerated?” question, lets compare a pond with no aeration, a pond that is under aerated and a pond with sufficient aeration.
A Pond with No Aeration: With no aeration present, the water is stratified (aka has a thermocline). Meaning that the water at the top is warmer and full of oxygen while on the bottom the water is cooler, nutrient rich and contains no oxygen. This causes the fish to habitat towards the surface of the pond. As the seasons change from the hot summer to cold winter, the pond goes through a process known as “turnover”. This is when the cooler water at the bottom of the pond, mixes with the warmer water at the pond’s surface. Since the rising cooler water contains no oxygen, the chances of a fish kill are imminent.
A Pond that is Under Aerated: When a pond is under aerated, the thermocline is not eliminated, only dropped further down towards the pond’s bottom. This can cause constant problems. As the bottom bubbler aerates, the bottom, nutrient rich water is lifted to the pond’s surface. These nutrients are now constantly available for algae to grow. More importantly, the water that is being lifted by the bubbler also contains no oxygen, thus increasing the possibility of creating turnover and killing the fish.
A Pond with Sufficient Aeration: You may ask, “Since the nutrients are still being brought to the surface, won’t an algae bloom and turnover still happen even if a pond is properly aerated?”
When an Aeration System is initially installed, it should be started at a slow pace to prevent creating turnover (See blog “When & How to Start Your Aeration System” for more information). As for algae, initially, when the nutrients are pushed towards the surface, algae will have the chance to bloom. As time progresses, however, the thermocline will be eliminated, the nutrients will be flushed out and the fish may now habitat the whole body of water.