GH is a measure of how much calcium and magnesium is in your water. Amazon swordplants, in particular, need to have calcium in water. Possibly, your city water is softwater with little calcium. If you are happy with your tank and plant growth, GH doesn't matter. If you think there's room for improvement, I would learn what GH is and find out what the hardness is of your city water.My water source is city, hose to be exact. I don't know what GH is.