How Aeration Works

Choosing an aeration system is a challenging task. So many versions of a system are available with large variations in price and claims. They are all designed, in general terms, with the same big picture items: a pump, airline, and a diffuser. I realize there are other items involved such as cabinet, valves, manifolds, or gauges, but in this article, I would like to discuss how the pump and diffuser work together in relation to proper aeration.

What Criteria Do Pond Owners Use to Make Their Decision?

The average pond owner is likely to start with price and what all comes with that price. Will it aerate a pond my size? Does the price match perceived valve? Who am I buying from and how can they help me after the sale. This makes sense and is the same approach I would take. If the product’s details and description fits the situation, there’s no reason not to move forward. However, there are finer details of a working aeration system to understand related to proper aeration. This will significantly change how you will choose an aeration system.

How Proper Dissolved Oxygen is Achieved in You Pond

Without an aeration system, the amount of dissolved oxygen (DO) drops dramatically every foot you go down in your pond. The top 1 – 2 feet of your pond generally will have good DO levels naturally because it’s exposed to wind and air. Wind creates water movement and the movement entraps oxygen. The winder the day, the deeper good DO is recorded. Most days though, proper levels of DO don’t go much beyond two feet.

Many pond owners believe proper DO levels are achieved by the bubbles created with an aeration system. While aeration systems technically do produce some DO, the bulk of proper levels throughout the water column comes from water movement. Essentially, circulation. An aeration system’s goal is to push the poor levels of DO at the bottom of a pond to the top, which in turns forces the good DO at the top towards the bottom of the pond. This creates the circulation motion: bottom to top, top to bottom, as illustrated below.

A quality and properly sized aeration system, along with strategically placing of properly designed diffusers (see blog on diffusers), will affect the entire pond and at a great enough force to maintain a proper level of DO throughout the pond, as shown with the blue arrows in the image above. Without quality movement as pointed out with the yellow arrows above, the DO doesn’t make it to the bottom or throughout the pond. Essentially, some of a pond will not being effected at all by the system’s performance. What you have in the case of the yellow arrows is turbulence at the surface, not proper circulation. It may look the same at the surface, but below is a completely different story.

When small pumps make bold claims of large operating depths, you likely end up with circulation as shown with the yellow arrows. A small pump must have minimal resistance to operate at great depths. What would be cause the minimal resistance? The type of diffuser installed! 

Along with pump size and diffuser design, diffuser depth is critical to proper aeration. The deeper a diffuser can be placed, the more surface acres it can aerate. For example, a diffuser placed at 25 ft. of depth and attached to a 1/4 hp piston pump can properly aerate approximately an one acre pond. Take that same set up and place the diffuser at 10 ft., you are down to about a 1/4 acre pond. There's just not enough water movement. It's like the drawing with the arrows. The more you move the diffuser to the surface, everything shortens up to the point where you go from the blue arrows to the yellow.