Wow that's a high PPM for filtered tap water. Hard. Listen to latewood you can't go wrong. Your meter sounds good, to break it down would be a meter that cost thousands. The best we can hope for are total TDS. My distilled is close to zero and my new RO unit is 15 PPM TDS. Start with nothing and add back what you need BUT your plant looks real good. Must have good stuff in your water.