Goldfish blowing bubbles at top of water?

There are a few reasons why goldfish might blow bubbles at the top of the water:

* Low oxygen levels: Goldfish need a lot of oxygen to breathe, and if the water in their tank is low in oxygen, they may come to the surface to gulp air. This is especially common in overcrowded tanks or tanks with poor filtration.

* Stress: Stress can also cause goldfish to blow bubbles. Stress can be caused by a number of things, such as changes in water temperature, pH, or hardness, overcrowding, or the presence of predators.

* Disease: Some diseases, such as swim bladder disease, can also cause goldfish to blow bubbles. Swim bladder disease is a condition that affects the goldfish's ability to control its buoyancy, and it can cause the fish to float to the surface or sink to the bottom of the tank.

* Temperature: Goldfish prefer cooler temperatures, ideally between 65 and 78 degrees Fahrenheit. If the water temperature rises above 85, goldfish can become stressed and start blowing bubbles.

If your goldfish are blowing bubbles, it's important to take action to determine the cause and correct the problem. If the cause is low oxygen levels, you can add an airstone or bubbler to the tank. If the cause is stress, you can try to reduce the stress by making sure the tank is clean and well-filtered, and by avoiding overcrowding. If the cause is disease, you can treat the disease with medication.

It's also important to note that goldfish that are blowing bubbles may be in distress and need immediate help. If you see your goldfish blowing bubbles, it's important to take action to determine the cause and correct the problem as soon as possible.