My new goldfish is gasping for air

If your fish is gasping for air something is clearly wrong. It can be ammonia (this is a waste product from your fish urine and decomposing food and plant matter).

Ammonia will be broken down by bacteria and create nitrite, this and ammonia is toxic to fish and other life in your tank. You can read more about this in the article on fishlore.com.

The end product of bacterial metabolism of ammonia and nitrite is nitrate (plant food). This is not toxic, unless the concentration gets high. To keep the nitrate down, you need to change some water every week.

When your fish gets ill the first thing to do is to stop feeding to get the bioload down; you need to take water tests to find the cause of the problem, it is often ammonia or nitrite poisoning that is the root cause for fish getting ill.

Poor maintenance of a tank will often result in problems for your fish. You need to vacuum the gravel about twice a month, change about 20% of the water each week and clean the filter when you can see the flow is reduced (use water from your tank when you rinse the filter material). Do not clean more than half of the filter material each time you do this.

A tank of only 20 liters is too small for goldfish (and most other fish). You will need a tank of 60 liters or larger for one single goldfish. More information about this could be found in this article on thegoldfishtank.com.

Gasping for air can mean a few things. First you want to check all parameters. You already checked ammonia, nitrite and nitrate. Check pH, hardness and temperature. Gasping usually means the metabolism is in over drive (too hot, stressed) or there is an issue with the gills (not enough O₂, irritation, infection, poor water quality). Eating bubbles is just a weird behavior in some fish and not recommended, try to prevent it and make sure you fish has plenty to eat but no left overs. Eating air bubbles can interfere with the swim bladder and force the fish to the surface.

Prevent your fish from getting stressed out, so don’t make water changes too fast. Rule out water quality as an issue. Next look for any irritation, infection or parasite on the gills. They could be swollen and red, tiny white dots, white cotton appearance, black tiny dots.