Distilled solves two problems at once and people only hear about the first. No white dust on leaves, and much less for a biofilm to attach to inside the tank.
If buying distilled water constantly is not realistic, a cheap filter jug is a middle option that noticeably reduces both. Not as good, considerably better than tap in a hard water area.
You can also tell which problem you have: white dust on nearby surfaces means minerals, a slippery feel inside the tank means biofilm. They need different fixes and people apply one to the other.