The Reason i ask is theres a lot of people on here who can barely afford proper lighting so there must be people who have used nothing but water, also depends whats in the tap water in your area/country.
My Plants are under a 600w hps in 25-27°c when the lights on and no lower that 21°c when off the have a small half dose of miracle grow every 2 weeks during Vegging with a tower fan to circulate air and there huge and healthy. There Amnesia Haze grown from feminized seeds by the way.