Distilled water and R/O water lack the minerals and salts that your frogs need to hydrate themselves. It is only safe for misting. If you use in your frogs water bowls. It will actually steal minerals/vitamins/and salts from your frogs and will cause severe health issues. If you intend on using R/O water for your frogs main water source it must have minerals and salts added to it. You can buy these additives like you can the conditionersat some pet stores.