This is entirely normal behaviour for Gouramis (within moderation). Gouramis are part of a group of fish called 'Labyrinth Fish' (Sometimes also known as 'Anabantoids'). These fish have a special 'lung' organ called the 'Labyrinth organ' which allows the fish to absorb oxygen through the blood stream in a similar fashion to that of lungs directly from the air instead of by passing oxygenated water through its gills. Other common fish which are part of this group are Betta and Paradise Fish.
Labyrinth fish are commonly found in lakes in Asia where the water has a low oxygen content necessitating the use of an organ to absorb oxygen from the air instead.
Perhaps this is a sign of poor water quality?
These fish do tend to be more resilient than other fish when it comes to water parameters but, as with any fish, good quality water is a must to maximise growth and life.
A few caveats
- 'Everything within moderation' - As the saying goes, if your fish are breathing excessively at the surface, something might be up. Check your water parameters, feeding regime and any other environmental factors that could contribute to general ill health.
- It is advisable to ensure there is some clear space between the water surface and the lid of the aquarium to facilitate the breathing of oxygen directly through air.
- Whilst Labyrinth fish can survive in lower oxygen environments, good oxygen circulation is still advisable.