Nico’s Nuggets: All About Water: Purity, pH & O2

Hi, Nico. I'm a rather new grower who has become totally enthralled by it. I absolutely love the Grow section of and have used you as a reference when seeking information. I have just purchased a water-storing tank that I fill with distilled water and have the following questions regarding it:

1. Would it behoove me to add an air stone into the tank to oxygenate the water?
2. Should I even be using distilled water?
3. What is the best way of monitoring a pH level, besides a pH pen and testing solution?
  – Many thanks, Crusto – via

Greetings Crusto! Thanks for reading and writing in.

I want to inform you that you are right where we all were when we first started growing cannabis – that is to say worried about the quality of water we were using on our precious plants. Well, rest easy, you need not go through the worry or the tiring efforts to supply your garden with the purest of water.

Distilled water is hard to come by. Of course you can buy it, but that will get quite costly for something you get relatively free from the faucet. And distilling your own water, which entails boiling and then condensing the steam, would be exhausting and impractical. Unless you know for a fact that there is something seriously wrong with your tap water, you need not fear it when it comes to your garden.

Still, some growers do prefer to put a filter on their water lines to filter out any larger particles coming through. Reverse osmosis filters are great for removing excess salts as well, but can take considerably longer to fill reservoirs and are often impractical for large-format grows. If you are worried about the quality of your water, using a standard tap filter on your faucet usually will suffice.

Oxygenated reservoirs supply large grow table gardens.

There have been plenty of studies over the years to support using both tap water and purified/ distilled water – and some even claim that unfiltered water is best because of the added mineral value. Speaking from experience – and from the immense access to growrooms and farms this job has afforded me over the years –  I can safely say that regular old tap water is fine.

Water filters are a good way to remove sediment and particles when necessary.

When it comes to pH, it is important to take measurements both before and after watering. First, measure the pH of your water. Then measure the pH of the run-off from your plant containers. It doesn’t matter what you use to make the measurements so long as your method is accurate. PH is important because it affects the nutrient uptake of nutrients by the plants. If the pH changes significantly in the run-off, this is usually sign of a problem with your medium and flushing may be necessary.

For soil or soilless mediums, you want your water pH levels to be between 6.0 – 6.5 before watering. For hydro systems that rely on rockwool or clay aggregate as the medium, a lower pH of between 5.8 – 6.2 is recommended. Pure water will always have a neutral pH of 7.0. It is important to remember that every whole number on the pH scale is 10 times more (or less) than the previous whole number, so each decimal point is quite significant. A pH of 3.0 is 1,000 times stronger (acidic) than a pH of 6.0. Growers should check their pH levels every couple of days, or whenever a new medium or nutrient is introduced into the grow system. Plants prefer slightly acidic water, which also answers the question a bit more accurately regarding distilled water vs. tap water.

And lastly, in regards to oxygenating your water tank with an air stone – this is never a bad idea. If you are able to do so, plants love water with high-O2 content. People often forget this fact, but the roots breath in oxygen while the rest of the plant (above ground) breaths in CO2. The added oxygen will help stabilize your pH levels and aid in nutrient uptake and plant development.

Thanks for reading everyone and remember: Grow… And help the world grow, too!

Top pic: Water is the life blood of any garden.

Got questions? Email 'em over to Nico at and be sure to put “Nico’s Nuggets” in the subject line!

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