(lovely things like Legionella. Not good at all.)
The warmer for the water tank accellerates any bacterial action. (further not goodness)
Because of this I always dump it out and dry it with forced air every morning.
The hoses get blown out too if they have any moisture built up.
Every week I disinfect everything with thyme oil, then rinse and dry. The water tank gets the vinegar treatment and thorough drying afterwards.