Yes you can grow VERY well with well water, even better than with city tap water. You do not need a filtration system!!! Water (be it well or city tap) has essential minerals in it that RO or distilled lack. Most notably Mg, Ca, Fe and Zn. Using RO water will end up in mineral deficiencies unless you supplement them, but why buy supplemental minerals that you'll get for free and in the correct ratios? City water has chlorine/chloramine and flouride in it, well water doesn't. I use my city tap water without filtration, have for years with no probs. The ONLY time I ever had a prob was when I first started out and believed some (OK, more than a few) Jackasses who told me I HAD to use RO or distilled water. I had Mg and Ca deficiencies to the point of losing all but 1 or 2 plants out of 30, over 2 grows.! Don't make that mistake! (Or if you DO make it, remember I told you so!!! LOL)