Type of water? Let tap water sit out?

Go with distilled water you can make your own but buying is not expensive. Now you can add the nutrients and not be affected by some random chemicals.

I use charcoal filtered tap water. The chlorine is best to let it sit out for about 2 days, or a small dose of ascorbic acid or vitamin c will also neutralize it. The amount need is very little please research for amount of water you are treating at a time.

It absolutely doesn't need to sit out, and letting water stagnate for 24-48 hours before use is not great, either. if your area uses chloramine, it won't matter either way. chloramine takes forever to evaporate by comparison to chlorine. Secondly the levels of chlorine or chloramine are so low, you will never see a difference. Some whacky esoteric context may be out there, but for most people this is not necessary. I have a higher ppm out of my tap than you do and never had an issue even with longer-term mother plants. The last 1.5 years i've been using soft water due to convenience of nearest faucet. Was worried at first, but after a fwe grows it clearly is irrelevant too. now, if you ever go gangbusters with lab-precision, co2, temp, rh control etc... then you might want to bother with filtered or RO water, if trying to squeeze out 100% of return from all that sophistication... where as if just loosely avoiding extremes, feeding wll and giving max dli for ambient co2, it's not so important. you won't ever need that extra headroom for fertilizer to match an elevated metabolism of a plant swimming in extra co2.

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Hey Growmie, I myself use tap water, I was once told if it is good for you to drink then it's good enough for the plants to drink, as mention though you are supposed to let it sit for about 24 hours so that the chlorine can evaporate from the water because it could be harmful to the microbes in your soil.

I allow my water to sit out so as to evaporate the Chlorine. I keep a small bubbler in it to accelerate the process. Chlorine will kill bacteria in your soil. If you aren't using microbs in your soil, then you don't need to worry about it. I use Mykos Products so i need to gas off my water. Check your ppm of your tap water so you know your baseline, and make the adjustments to your nutrients accordingly (don't make the mistake i did) If your ppm is 220 out of the tap, then based on your nutrient feed chart, you could omit the calmag if your chart calls for its application. Hard water is calcium and magnesium present in the water about a certain threshold, though i don't recall the value where they call a water hard and soft, 125ppm perhaps? I can't remember. You can look on your city's website or whoever provides and treats the local drinking water and they should have a break down of the water and whats in it. I wouldn't recommend using RO water, It can produce unstable pH values, and it's really not necessary. RO water is for humidifiers, not plant roots. Hell RO water isn't even recommended for humans to consume.

Tap is generally ok to use. If your water is chlorinated you have to let it evaporate off. If you use well water, super hard water can affect nutrient uptake. Don't use water softened with sodium.