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The importance of water quality in hydroponics & aquaponics

With water being the main component in hydroponics, the quality of it is incredibly important. Many people assume that if you are on a municipal water supply, you can just add your nutrients, and you’re good to go; in some cases, that can be true. However, some things in municipal water or your well water may need to be accounted for.

This blog by Zipgrow focuses on the basics of quality in terms of best cases and operations for hydroponic growing both on a hobbyist and commercial scale. 

Water quality has a lot to do with the performance of your crop. Quite often, we hear about deficiencies in crops from customers or farmers, and it’s seldom an actual lack of nutrients but almost always the availability of nutrients to the plant. The water quality will affect the uptake of nutrients by the plant. Hard water (water that has high mineral content) is an excellent example of this. If your city has hard water or you are on a well system, it can really restrict the availability of nutrients to your plants.

Growing in soil v’s hydroponics
When growing in soil, all the critical nutrients and minerals are bound to the soil through a charge; plants send out lateral fibrous roots when they encounter these nutrients and want to take them up. They release H+ and OH-  ions that balance out the charge and help release that mineral to the plant. The plant can take these minerals up and move them across root membranes, releasing the mineral from the soil. 

In hydroponics, it’s different because we don’t have all that soil holding these nutrients close to the root, and the plant is not constantly searching for nutrients because water is always moving and available. We need to ensure that these nutrients are highly available throughout the water solution because there is no solid holding them by the roots. The ion exchange doesn’t really happen in the same way; it’s not unlocking it from a soil particle that’s negatively charged but taking up nutrients that are delivered via solution. Hydroponic crops still release ions (this is why pH changes!) but not in the same way as they would in solid. So to replace that in hydroponics, we constantly supply nutrients to the root zone in the solution. 

Not all water is equal
Because all the nutrients are being delivered via solution, the incoming water quality is essential and something you must always consider. 

Reverse Osmosis (RO) Systems
In any hydroponic system, it will make your life a lot easier if you have a reverse osmosis system that supplies your base water. RO systems come in various sizes depending on the size of your operation. They are a series of filters that remove larger particles and those that can’t be seen. This multi-stage process pushes the water through a specialized, semipermeable membrane. The results of which are water that’s as close to zero EC level as you can get, typically around  0.1 EC or less. 

EC is the measurement of the salts in the system. This gives you a blank playing field in terms of adding and measuring nutrients.

Municipal water can come in at up to 0.6-0.8 EC, so if you are adding in nutrients on top of that (without taking into account the original EC levels), you may be providing more nutrients than needed and could be harming your plants. 

RO systems can be relatively inexpensive for home use, through to costly systems for larger operations. In our experiences, many of the folks who spend months struggling with pH and artificially trying to lower it, reached the point where looking back, they wish they’d just installed an RO filter and avoided the cost and headache of fighting the fundamental chemistry of their system.

An RO system can be slow to process the water, so we advise that people have a separate reservoir/tank, so you have plenty of pre-filtered water when you need it. 

What’s in the water? Knowing your municipal water quality.
Knowing the quality of your existing water supply is a good idea. You can send your water off for lab testing; many local universities will offer that as a paid service. They will give you a full breakdown to know your carbonates, any heavy metals present, and the pH of your incoming water. Especially for commercial growing, you would want to get a professional water panel done. It’s an inexpensive way of making sure everything is safe. Information is often generally available too within your own municipality.

Let it rain… or should you?
For sustainability reasons, many hydroponic growers will consider using rainwater in their tanks. This can work well, but you need to be conscious that rainwater tends to be pretty acidic; it may also carry diseases, parasites, or pathogens. If you use rainwater for your hydroponic systems, there is a high risk of things like root crop diseases and fungal and bacterial diseases, and algae. It’s a good idea to have a disinfection plan or water filtration process like an RO system.

Water temperature
Basic concepts that apply in traditional growing in terms of water temperature also apply in hydroponic growing; too low, and you will shock your plants; too high, you create an environment perfect for algae, bacteria, and many diseases.

You would want to curb that environment because once those things get into your system, it’s impossible to get them out without a full system shutdown to scrub everything out.

A general rule of thumb is that your water temperature should be a couple of degrees colder than your air temperature. Usually, this is easy to maintain without much effort. 

The down low on D.O and water aeration
Understanding why you need to aerate is crucial. It maintains water temperatures and prevents stagnant water and things from overheating. In commercial growing, it also helps release some things from the water too, such as high levels of nitrogen gas. Another term you often hear in hydroponics, specifically aquaponics, is D.O. 


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