I have a aquabuckets 4 site system by Hydro West 600 Watt hps lights. My question is do I really need to change the water every week. I had a small problem with slime but put a five hundred gallon aquarium filter in reservoir and no problem. No smell no slime. Also almost to flowering stage is it to late to top or use lst. There is no way to just change reservoir water and don't see the point when everything is fine. Help and suggestions please. Thanks