Why Is Your Protein Skimmer Producing Microbubbles?

Seatorch Australia

Aug 10, 2026

Why Is Your Protein Skimmer Producing Microbubbles?

Protein Skimmer Microbubbles: What Are They and Why Do They Happen?

If you've ever looked into your aquarium and noticed thousands of tiny bubbles floating through the water, you may have wondered:

Why is my protein skimmer producing so many bubbles?

Microbubbles are a common part of aquarium filtration, particularly with protein skimmers. In most cases, they are not a sign that your skimmer is faulty.

Understanding what microbubbles are — and why they appear — is the first step toward solving the problem.

What Are Microbubbles?

Microbubbles are extremely small air bubbles suspended in the aquarium water.

They are much smaller than the normal bubbles you might see around an air stone or the surface of an aquarium. Because of their tiny size, they can remain suspended in the water for a long time and may travel through the sump and eventually into the display aquarium.

Why Does a Protein Skimmer Produce Bubbles?

The production of fine bubbles is actually the main principle behind protein skimming.

A protein skimmer mixes aquarium water with a large amount of air, creating thousands of tiny bubbles inside the reaction chamber.

Organic compounds and dissolved waste in the aquarium water attach to the surface of these bubbles.

As the bubbles rise, they carry these organic compounds toward the collection cup, where they can be removed from the aquarium system.

In simple terms:

Water + Air → Fine Bubbles → Organic Waste Attaches → Foam → Waste Removed

So, bubbles inside the skimmer are completely normal.

The problem occurs when those bubbles escape the skimmer and enter the aquarium system.

When Do Microbubbles Become a Problem?

A small amount of microbubbles leaving the skimmer may not be a serious concern.

However, excessive microbubbles can become noticeable when they:

Travel from the sump into the display aquarium
Cover aquarium glass with tiny bubbles
Collect on corals, rocks or equipment
Make the aquarium appear cloudy
Create excessive turbulence around the sump
Continue for an extended period

If you see a large amount of microbubbles entering your display tank, it is worth investigating the cause.

Why Are New Skimmers More Likely to Produce Microbubbles?

One of the most common situations is a brand-new protein skimmer.

New skimmers have extremely clean internal surfaces. During the first few days of operation, the acrylic and internal components have not yet developed the thin biological film that naturally forms during aquarium operation.

Because of this, the skimmer may behave differently from an established skimmer.

You may notice:

Large amounts of microbubbles
Unstable foam
Foam that rises and collapses repeatedly
A collection cup that behaves unpredictably
More bubbles escaping through the outlet

This is commonly known as the skimmer break-in period.

Depending on the skimmer and aquarium conditions, the break-in period may take approximately 3–14 days.

What Else Can Cause Microbubbles?

1. Incorrect Water Depth

Every skimmer has an appropriate operating water depth.

2. Incorrect Skimmer Adjustment

If the skimmer is adjusted too "wet," the internal water level can become too high.

3. Dirty or Blocked Components

Salt creep, algae, calcium deposits and debris can affect water flow through the skimmer.

Components such as the outlet, bubble plate, pump and air intake can all influence skimmer performance.

4. Recent Aquarium Additives

Some aquarium products can temporarily change the behaviour of a protein skimmer.

Examples include:

Coral foods
Bacterial supplements
Water conditioners
Epoxy
Medications
Other water treatments

These products may temporarily increase foaming or microbubble production.

5. Water Flow Around the Skimmer

Sometimes the skimmer is working normally, but the surrounding sump flow carries microbubbles toward the return pump.

If the return pump draws these bubbles into the return line, they can eventually appear throughout the display aquarium.

6. Air Leaks

A loose fitting, damaged O-ring or poorly sealed connection around the pump or air intake can introduce unwanted air into the system.

This can cause unstable or excessive bubble production.

In many situations, the skimmer is simply responding to its environment.

The cause could be:

New skimmer → Water depth → Adjustment → Maintenance → Aquarium additives → Water flow → Air leak

Identifying the cause is much more effective than continuously changing the skimmer settings. In next article, we will taking step by step on how to troubleshooting it. Stay turn and stay salty.