Grobo recommends that you use Reverse Osmosis (RO) or Distilled water.
This is for a few reasons:
- Local municipalities have added compounds in the tap water that plants don’t use. This includes things like chloride.
- RO and Distilled water is less hard and has less salt content - providing optimal conditions for your plant to grow
Note: You can use tap water and the Grobo will adjust dosing level as much as it can, but it can have severe impacts on the viability of your grow depending on your local municipality's water contents.