Are the Bubbles in My Aquarium Normal?

Seeing bubbles or foam in your aquarium can be puzzling, but it’s usually harmless and sometimes even beneficial. Bubbles can form for various reasons—here’s a breakdown of the common causes and what each means for your tank.

• Air Pump Bubbles
  One frequent and harmless reason for bubbles is the use of an air pump. These devices introduce air into the water through tubes, often connected to air stones, sponge filters, or decorative bubblers. The bubbles should appear clear and typically pop when they reach the surface. CO₂ injection systems in planted tanks may also create small, harmless bubbles that dissolve quickly.

• Tiny Bubbles After Water Changes
  Water changes, especially in colder weather, can result in tiny bubbles coating tank surfaces. When cold water from pipes is warmed in the tank, dissolved gases escape, forming bubbles on the glass and décor. This is temporary, and the bubbles will generally disappear after a few hours. However, large or sudden temperature changes can sometimes disrupt water stability, so monitor your fish after big water changes.

• Foam from Treatments or Medications
  Some fish medications can cause temporary foaming by thickening the water. Normally, bubbles would burst quickly, but with certain treatments, they linger. If you spot bubbles with an oily sheen, it could be a sign of soap or another contaminant, which is dangerous for fish. Be sure to thoroughly rinse any equipment before returning it to the tank.

• Surface Film or Biofilm
  A biofilm can sometimes develop on the water’s surface, trapping bubbles and preventing them from popping. This layer may result from fish food oils, or even oils from hands, and can disrupt the gas exchange fish need. Increase surface movement by directing the filter flow toward the top or adding a sponge filter to break up the film and improve oxygenation.

• Foam from Excess Ammonia
  High ammonia levels in tanks with heavy waste buildup or uneaten food can cause foaming. Excess ammonia often creates foam when bubbles form from a sponge filter or air stone. If you see foam without any medications used, check ammonia levels and reduce waste buildup to keep the water safe.

• Bubble Nests from Fish
  Some fish, like bettas, naturally create bubble nests as part of their breeding habits. The male fish uses saliva to create bubbles, forming a nest where he can protect his eggs. These nests usually sit in a calm area of the tank and are completely natural.

 Bubbling Plants

• When aquarium plants undergo photosynthesis, they release oxygen, creating bubbles on their leaves. This “pearling” effect is a good indicator of a healthy plant environment. Even algae can produce bubbles through photosynthesis, which adds oxygen to the tank.

Whether bubbles in your aquarium are good or bad depends on their cause. Understanding these signs can help keep your tank environment balanced and your fish happy. For more tips on aquarium maintenance, stop by our store and chat with an aquarium expert.