May 03, 2024

What Size Pond Aerator Should I Buy for My Pond?

Choosing the right size pond aerator to sufficiently turnover your pond.

Subsurface aeration is the best way to mechanically initiate the transfer of oxygen into a pond. Although micro bubbles – created by air flowing through a diffuser – add some dissolved oxygen, the greatest transfer occurs as water circulates to the surface. Water at the surface absorbs oxygen from the atmosphere and then circulates back to the bottom of the pond. Turning over the pond – the process of moving the entire volume of water to the surface periodically – creates an oxygen rich environment at all depths. In turn, fish can thrive, and conditions are right to break down organic matter and reduce/ prevent algae blooms.

Given the importance of water circulation, choosing the right size pond aerator is critical for getting the best results.

Pond Aerator Sizing- 2 methods

If you are planning on 2 diffusers or less with a water depth of 6 feet or less, the recommendations in the sizing table (method 1) below should be a good starting point, but few applications are black and white.

Often the amount of air flow required is dictated by the number of diffusers needed to mix the pond. Below the table below we dive in to how to size a pond aerator based on the number of diffusers (method 2).


Method 1: Pond aerator sizing table


pond aerator

*If breeding specific types of fish, we would recommend consulting with an aquatic specialist before selecting a pump as certain breeds require different levels of oxygen


Method 2: Sizing a pond aerator by the number of diffusers

Every pond is unique in size, shape, and depth. Figuring out the number of diffusers needed to mix the entirety of the pond and working backwards can be a prudent strategy. For example, if you have a kidney shaped pond, you probably need at least 3 diffusers. Some ponds may need 4 if they have multiple coves.

Pond Aerator Sizing Steps:

  1. Choose the number of diffusers based on the shape and size of your pond.
  2. Identify which model diffuser you are going to buy. Manufacturers typically publish how much air flow is needed to “self-clean” – the amount of air flow that will keep the pores open and free of biological growth. Somewhere in the 30-40 LPM (liter per minute) is common and creates good circulation.
  3. Figure out the back pressure of your system (water pressure + diffuser backpressure + tubing friction loss). For a detailed step-by-step process, check out our article:
  4. Once you have figured out the backpressure of the system, review the pond aerator performance curves to determine the total amount of air flow. Start with the aerator recommended in the Pond Aerator Sizing Recommendation Table and bump up to the next size if needed. Pressure and flow have an inverse relationship – if one goes up, the other goes down. Performance curves are available on our website and are explained in the backpressure article.
  5. Divide the number of diffusers needed by the total air flow. Choose the pump that exceeds the amount of flow per diffuser suggested by the manufacturer.


To keep things simple, let’s assume that I’ve already gone through step 3. I’ve determined that my total backpressure is 3.8 PSI. I have a ½ acre pond that is about 8’ and would like two diffusers that need 30 LPM to “self-clean”. I’m looking at the HP-80 performance curve first. In the graph below, the red vertical line (from 3.8 PSI) hits the green curve at about 2 CFM or 55 LPM. If you were to split the flow to two diffusers, you would get about 27 LPM to each diffuser, which is lower than the target.

pond aerator

I’ve now bumped up to the HP-100LL (see graph below). At 3.8 PSI our flow is closer to 80 LPM, so each diffuser would get close to 40 LPM. The HP-100LL is what I’d recommend.

pond aerator

If I decided to bump it up to 3 diffusers for some reason, the HP-100LL wouldn’t be enough flow. Let’s look at the HP-120LL graph below. At 3.8 PSI, the HP-120LL puts out about 100 LPM, so that would be my choice if I needed 3 diffusers.

pond aerator

If you have any questions about choosing the right size pond aerator, please give us a call at 734-944-5032 or email us at

May 03, 2024

Posted in:

Pond & Aquaculture

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