Water quality in hydroponics and aquaponics is vitally important to understand and appreciate. Not only is it considered the most essential component of your system, but it is the lifeblood of the entire operation. Without good water quality, you can’t grow anything.
While water itself comes down to just a handful of parameters — pH, temperature, oxygen, alkalinity, and nitrogen — it’s those parameters that must be maintained and manipulated to meet the unique needs of your intended end product. And to do that, you need to be aware of what each parameter does and how each one affects your system.
Table of Contents
- Water Quality Parameters (pH, Temperature, Oxygen, Water Hardness, Total Nitrogen)
- The Type of Water You should Use (Tap Water, Filtered Water, Rainwater, Aquifer Water)
- How to Change Your Water’s pH (How to Raise and Lower pH in Your System)
- How to Test Your Water (Quick Overview of testing and testing materials)
- What to do About Algae (What algae is and what to do about it)
Considerations for Hydroponics
When it comes to water quality in hydroponics, your biggest concern is keeping your fruits and vegetables as happy and healthy as possible. That means that your water quality (pH, EC, temperature, etc.) should match the specific needs of your fruits and vegetables. Pay attention to each plant’s specific needs and adjust your water quality to meet those needs.
Considerations for Aquaponics
Aquaponics is a little more complicated than hydroponics so your water quality considerations are a little greater. In aquaponics, it’s all about finding a balance between your fish, your plants, and your bacteria. If one of those groups isn’t performing correctly, then your whole system can go off the rails.
If you’re planning to grow aquaponically, then you need to understand that compromise is everything — each component of your system has a very specific tolerance range and must meet certain water quality parameters. Therefore, because each organism — plants, fish, and bacteria — have their own needs, you’ll need to adjust your water quality to meet the best possible outcome for each group.
BLUF, in an aquaponics system, it’s impossible to have every organism functioning at its optimal and most productive level simultaneously. The trick is to find balance and make necessary sacrifices!
Understanding Water Quality Parameters
If you’re going to get into aquaponics and hydroponics (to include aeroponics), you need to understand your water quality parameters and what exactly each parameter entails.
1. pH
Understanding and adjusting your pH is extremely important in hydroponics and aquaponics, and although it may sound intimidating (especially for those of us who struggled in chemistry), it’s probably not as complicated as you think. When it comes to your responsibilities, all you really need to understand is the pH scale and how to read it.
In essence, pH is a measure of how “acidic” or “basic” your solution is on a 14 point scale. If your water has a pH of 7, then it’s neutral; if it’s below 7 then it’s considered “acidic,” and if it’s above 7 then it’s considered “basic.” Your goal is to keep the water inside the appropriate pH range (as applicable to your plants or fish).
2. Temperature
Temperature is vitally important for your setup and you need to adjust and maintain it just like everything else. If you’re growing indoors, temperature can be manually maintained by you, but if you’re growing outside in the elements, then you need to pay attention to your climate and adjust accordingly.
For an outdoor hydroponics setup (one where you can’t manually regulate the temperature), you need to grow plants within your hardiness zone that are appropriate for your climate. Here’s a quick list of the best hydroponic plants (make sure to pay attention to their temperature ranges).
And on another important note, if you’re growing aquaponically, then you need to do your best to match plant temperatures with fish temperatures. For example, okra and tilapia both do well in warm climates; thus, it’s best to pair these two up if possible.
3. Oxygen
First and foremost, if you ever see the words “DO” used to describe oxygen, that acronym is referring to “Dissolved Oxygen” and it describes the amount of oxygen that is present within water. And make no mistake, it’s important to understand and regulate as you monitor your system (especially with aquaponics).
Oxygen (or rather DO), is essential for every component of your system — plants, fish, and bacteria — and out of all the water quality parameters, it has very immediate and drastic consequences if not maintained. For example, if you’re experimenting with aquaponics and your water’s DO drops suddenly, then your fish will probably die within a few hours.
To maintain your oxygen levels, you have two options: (1) you can buy a DO measuring device (which are sometimes expensive), or (2) you can simply observe your setup to see how your fish are behaving and how your plants are growing. If either of these seems unusual or out of the ordinary, then adjust your aerator’s oxygen flow and see if things change.
4. Water Hardness
When it comes to water hardness, there are two types: general hardness (GH) and carbonate hardness (KH), also known as alkalinity. General hardness (GH) refers to the amount of calcium, magnesium, and iron ions present in your water while carbonate hardness (KH) refers to the amount of carbonates and bicarbonates dissolved in your water.
For your system, you’ll only need to worry about carbonate hardness (KH) because it has direct impacts on your pH. To summarize this and put it in as simple terms as possible, KH essentially acts as a buffer to your water’s pH and keeps it from dropping too quickly. And because rapid changes in pH are stressful to your system (especially in aquaponics), you’ll want an adequate amount of KH to prevent your water’s pH from rapidly dropping and becoming too acidic.
The good news is that just like everything else, KH can be controlled. Typically, all you have to do is replenish your water (because KH is naturally present in water, replenishing your water should also replenish your KH).
However, in the event that you’re using rainwater for your system, you will have to add external sources of carbonate to keep the system stable because rainwater is naturally acidic and low in KH.
5. Total Nitrogen
Nitrogen is a requirement of all life and it is an essential component of your system. And while it’s certainly an element within hydroponics, it’s more of a concern for aquaponics due to the system’s reliance on fish.
For an aquaponics setup, nitrogen originally enters the system through your fish food. When you drop fish food into your tank, some of it is eaten by the fish for protein and growth, and then some of it is released by the fish in the form of fish waste (aka fish poop and fish urine). This “waste” comes out in the form of ammonia (at least mostly) where it is nitrified by bacteria and becomes nitrite and nitrate. And this is where things get interesting.
Generally speaking, nitrogen compounds are pretty toxic for fish but really healthy for plants. So, there needs to be a balance. Therefore, in any aquaponics setup, it’s best practice to keep nitrite and ammonia levels as close to zero as possible. This can be done through testing and proper monitoring.
What Kind of Water Should You Use?
When it comes to what “type of water” to use, there are really only 4 options available to you: tap water, filtered water, rainwater, and aquifer (cistern) water. If you’re a beginner, think about the advantages and disadvantages of each option before picking one. Although every option will technically work, one may be more suitable to your needs, ability, and setup.
1. Tap Water
Tap water is the most common type of water used in hydroponic and aquaponic setups. It’s easy, readily available, and can come straight from the hose. However, even though it’s probably your easiest option, you still need to be mindful of some of the drawbacks.
Tapwater, at least initially, usually contains chlorine and chloramines, chemicals used to treat water. And unfortunately, while chlorine may make the water consumable for humans, it’s very toxic for your plants and fish.
So, for purposes of your system, if you’re going to use tap water, make sure to first test it with a chlorine test kit. If high chlorine levels are detected, you have two options: (1) you can use dechlorinating chemicals such as charcoal filtration, or (2) you can simply store the water before you use it and allow the chlorine to naturally dissipate into the surrounding atmosphere. Typically, it’s best to let your water sit for 48 hours, but if you’re in a hurry, you can also use air stones to aerate your water and make it dissipate faster.
A good habit and rule of thumb is to never replace 10 percent or more of your water without testing it first and removing the chlorine. BLUF, for every new source of water, just remember to test it.
2. Filtered Water
Filtered water, as you probably expected, is very safe to use within your system. Because filtered water goes through a filtration process (hence the name filtered), it probably won’t contain any unwanted metals and ions, making the water safe and easy to change if necessary. However, just know that because the water is often deionized, it may lack sufficient hardness and should be buffered when applicable.
The drawback, of course, is that most households don’t have filtered water just lying around all the time. And if your setup needs a large amount of water, filtered water might be a little short in supply.
3. Rainwater
Rainwater is a great water source for your system. If you can properly collect it using rain barrels (explore our hydroponic rain barrel guide if you want to learn more), you’ll find that it usually has a neutral pH, low hardness, and near-zero salinity. Additionally, it’ll save you lots of money and has multiple environmental benefits.
However, the one thing to look out for when using rainwater is the acidic aspects of it. Rainwater will sometimes have an acidic pH, forcing you to increase the KH to correct it.
4. Aquifer or Cistern Water
In the rare case that you’re planning on using aquifer or cistern water, the quality of it will greatly depend on the aquifer’s bedrock. If it’s sitting on limestone, it may have high hardness. Or, if it’s near saltwater, it may have high salinity. Regardless of the bedrock, however, just remember to test it (just like everything else here).
If everything looks good, then it’s ok to use. If something is off, then take the appropriate steps to adjust the water.
How to Manipulate and Change Your Water’s pH
Changing your water’s pH isn’t all that complicated, but out of all of the water quality parameters in hydroponics and aquaponics, it’s what you’ll spend the most time on. The good news is that once you’ve adjusted it a couple of times, you should get the hang of it and understand how it works. Here’s how to properly raise and lower your pH:
How to Lower Your Water’s pH
If you find that your water’s pH is too basic, you’re going to want to lower it using acid. To do this, all you need to do is add one of three acid products to your reservoir: phosphoric acid, sulphuric acid, or nitric acid. For beginners, just stick to phosphoric acid. It’s safer, does a better job, and can be found at any supply store.
One thing to keep in mind here is that acid, regardless of type, is pretty dangerous and can shock your system fairly easily. As a general rule of thumb, it’s better to add acid to a separate body of water, get the pH right, and then add the newly treated water to your fish tank (aquaponics) or nutrient-rich water tank (hydroponics).
Additionally, for aquaponic systems, just know that having to lower your pH is actually quite rare. Because fish naturally create an environment with nitrification and respiration involved, your water should naturally acidify. Only add acid if it’s absolutely necessary.
How to Raise Your Water’s pH
If you find that your water’s pH has dropped below 6, then your going to want to increase your water’s base/carbonate hardness. To do this, you can add in potassium hydroxide, calcium hydroxide, calcium carbonate, or potassium carbonate to your system. However, just like adding acid, it’s best to adjust your pH slowly over time so you don’t shock your system.
Another option, and more natural option, is to stuff natural calcium carbonate products — eggshells, limestone grit, and seashells — in a porous bag inside your tank. Your pH should increase within a few weeks and then you can simply remove the bag from your system once the required pH has been met.
How to Test Your Water
As you’ve probably realized, testing your water regularly is essential for any hydroponic or aquaponics setup. It will tell you exactly what’s wrong and what needs to happen.
If you’re a beginner, you need to test the water about once a week. That includes testing for pH, carbonate hardness, water temperature, and nitrate. If you can maintain these parameters, your system should be relatively balanced.
But how do you actually go about testing your water? The best way to test your water is to simply read and follow the directions on the bottle or kit. Whatever testing kit you purchase, it should contain fairly decent directions that are specific to the product. Follow the directions and guidelines and you should be good to go.
However, if you’re wondering what kits you’ll need to actually do the testing, here’s a quick list of potential products:
- All-In-One Freshwater Test Kits
- pH Meter Tester
- pH Test Strips
- Nitrogen Test Strips
- Dissolved Oxygen Meter
- Water Tank Thermometer
- Hardness Test Kit
- Total Dissolved Solids (TDS) Meter
- Water Tank Heater
- Chlorine Test Strips
What to do About Algae?
Whenever water, sunlight, and nutrients are combined, you’re guaranteed to find algae. And algae, despite a couple of benefits here and there, should be avoided at all costs in both hydroponics and aquaponics. Ultimately, algae is problematic for a few reasons:
- First and foremost, algae can cause blockages in your system and clog your filters, especially around openings and transition points.
- Secondly, algae will compete with your fruits and vegetables for nutrients, leaving your plants with less than ideal nutrition.
- Thirdly, while algae will produce DO during the day, it’ll consume DO at night. If you have an aquaponic setup, this will cause your fish to die.
To prevent algae growth, all you have to do is shield your tank or reservoir from direct sunlight. Make sure that it’s shaded, covered, and protected at all times and you shouldn’t have any problems.
Conclusion
Before you grow anything in hydroponics or aquaponics, make sure you’re aware of the water quality parameters and what they entail. While you truly won’t understand them until you physically start building your system and growing your vegetables, it’s never a bad idea to get educated before you start. After all, your plants will thank you for it and kindly return the favor with full, delicious-tasting produce!