I've had a pair of Pearl Gouramis and another pair of Opaline Gouramis for a few months now and, unlike any of my other fish (Tetras, Rainbow, Loaches), they spend time at the surface breathing the air instead of allowing the water to pass through their gills. 

Is this an issue or is this expected behaviour in a Gourami? Perhaps this is a sign of poor water quality?

<img src="https://adhenderson.co.uk/img/gouramiSmall.gif" />