What nutrients work with RO water?
Where to Get RO Water
Other growers use RO to “start fresh” as far as water is concerned. With RO water, you know exactly what you’re dealing with! There is nothing in RO water that you didn’t put there yourself.
Calcium & Magnesium Supplements
When using RO water for growing cannabis, it is important to use a Cal-Mag (Calcium and Magnesium) supplement alongide your regular cannabis nutrients. This is because you need to make up for some of the trace minerals that are normally found in regular water.
I like the General Hydroponics Flora trio plus their Cal-Mag supplement Calimagic.
As long as you add extra Cal-Mag, any quality cannabis nutrients should work well with RO water.
Many of the cannabis growers who choose to use RO water do so because, for one reason or another, their local tapwater is not suitable for growing cannabis.
CaliMagic is a popular Cal-Mag supplement from General Hydroponics, but other Cal-Mag supplements (made for plants) will also work.
These microbes exist in healthy soil.
The only solution to this, unless you gather pure rainwater direct from the sky rather than from roof runoff, is to use reverse osmosis water.
Your water consumption goes up, which may generate extra expense every crop cycle.
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But chlorine and chloramine decrease or eliminate beneficial microbes, depriving your marijuana roots of valuable biological enhancement.
This costs extra money every season, if you pay for water.
Some marijuana growers try to get by with tap water or well water instead of reverse osmosis water.
Municipal water almost always contains chlorine and/or chloramine.
Despite all the toxic warnings presented about the potential dangers of chlorine and its byproducts, one type of water filtration can do more harm than good; not harm to you, but to your local water supply. Specifically, small-scale reverse osmosis water filtration units waster immense amounts of water for each gallon of clean water they deliver.
Reverse osmosis uses high pressure to force the natural process of osmosis to happen in reverse. Normally, water molecules flow from one side of a semipermeable membrane that has a low concentration of solutes (the contaminant) to the side that has a high level of solute. Without any input of energy, the two sides would eventually equilibrate until both sides have an equal concentration. In reverse osmosis, the system uses high pressure to form the natural process to happen in reverse, meaning clean water flows from the dirty side to the clean side. However, water needs to continue to flow on both sides for the process to work, meaning some water is always wasted.
Industrial-sized reverse osmosis systems can create extremely high pressures meaning very little water flows to waste, and up to 90% can get recovered. Small, under-sink an even whole-house units can’t generate nearly the same amount of pressure, and only recover around 15% of the water they consume; the rest goes to waste.
Why do growers want to remove chlorine (ahem, chloramine) from their water? Chlorine kills microbes, a property that presents a serious issue for growers that take advantage of beneficial fungi and bacteria. Some evidence also indicates that chlorine in any form may stunt root growth in plants. Chlorine also reacts with organic compounds present in tap water to form trihalomethanes, toxic chemicals that can also stunt plant growth, be toxic to beneficial microbes and may even accumulate in the cannabis buds that you end up smoking.
Grow bibles all recommend using filtered water for obvious reasons, but be careful picking your filtration method. Any reverse osmosis water filtration unit smaller than an industrial-scale unit wastes three to seven times the clean water it delivers! Especially if you live in a drought-stricken state like California, you should use RO’s water-efficient alternative: whole-house activated carbon filtration.
Chloramine does not evaporate as readily from water as does chlorine. This is annoying for people who want to remove chlorine without having to filter, but be thankful for this. Chloramine’s poor rate of evaporation means its disinfecting properties stick around for longer, meaning won’t get sick from some water that’s been sitting around in a water main for a week.