This does really show the importance of run-off!
That is the stuff left behind in the media from evaporation too. It will build and build in the media unless there is adequate run-off to flush it out.
When it forms on the sides of the pot like that it is not really a problem, but does suggest that watering frequency may be too low.
When you think about water leaving the pot, it does so in two ways 1. Evaporation and transpiration, 2. run-off. The salt stains suggest that you might want to increase run-off relative to evaporation and transpiration. The best way to do this is increasing frequency, however, increasing quantity would be another (somewhat inferior) solution.
That said, it isn't really a problem and will not harm your plants. You don't need to remove it.