Water Quality
The water you use for your system is important as it will be used to transfer the nutrients to your plants. For hydroponic systems you would need to add a special blend of hydroponic nutrients to your water. If your water already contains nutrients, impurities, chemicals, or any other items then that will be mixed together with the special blend of hydroponic nutrients. This combination might negatively affect the growth of the plants. To avoid this situation it is best to use distilled water, deionized water, or water filtered through Reverse Osmosis (RO) as these do not contain any nutrients, impurities, chemicals, or solids.
Types of Water Suitable for Hydroponics (Suitable Water Type)
Distilled Water
Deionized Water
Water Filtered through Reverse Osmosis (RO)
Types of Water not preferred for Hydroponics
City Water
Drinking Water
Well Water
(this is not a complete list)
The following are variables that should be monitored in Hydroponics:
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Electrical Conductivity (EC)
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Total Dissolved Solids (TDS)
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Power of Hydrogen (pH)
The previous and following are variables that should be monitored in Aquaponics:
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Hardness (KH)
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Temperature
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Solids
Electrical Conductivity (Ec)
In Hydroponics this is used to measure the amount of nutrients in;
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the original water source being used
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0-10 S/cm
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the water mixed with hydroponic nutrients (*see Hydroponic Nutrient Suppliers' recommendation)
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for example the value for Leafy greens: *800 - 1200 S/cm
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Since Ec only measures the amount of salts in the liquid, it does not tell us what individual nutrients are present. To make a good hydroponic mixture you would use a Suitable Water Type and add the Hydroponic Nutrient Suppliers' recommended nutrients. This way you can assume that the nutrients in your mixture are suitable for your plants.
The Ec value is normally 2 times the TDS value, which is measured in "ppm." The Ec value is normally measured in "S/cm"
Total Dissolved Solids (TDS)
In Hydroponics this is used to measure the amount of nutrients in;
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the original water source being used
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0-5 ppm
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the water mixed with hydroponic nutrients (*see Hydroponic Nutrient Suppliers' recommendation)
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for example the value for Leafy greens: *400 - 600 ppm
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Since TDS only measures the amount of minerals, salts, or metals dissolved in the water, it does not tell us what individual nutrients are present. To make a good hydroponic mixture you would use a Suitable Water Type and add the Hydroponic Nutrient Suppliers' recommended nutrients. This way you can assume that the nutrients in your mixture are suitable for your plants.
The TDS value is normally half the Ec value, which is measured in "S/cm." The TDS value is normally measured in "ppm"
Power of Hydrogen (pH)
The pH level refers to the concentration of hydrogen ions in a solution. This tells you if something is acidic or basic. The pH scale goes from 0 to 14 with values from 7 to 0 getting more acidic and values from 7 to 14 getting more basic.
Plants will need the pH value to be in a certain range to grow properly. For example, the pH range for most vegetables is 5.5 to 6.5.
If you use a Suitable Water Type the pH can range from 6 to 7. pH levels can be adjusted with chemicals. For example, you can use lemon juice or a hydroponic "pH down" solution to lower the pH.
The pH level can be measured by the use of a simple pH test you can find at the local pet shop or pool store. There are also small low cost meters that can be purchased.
In Aquaponics:
The pH level has an effect on many other variables in the quality of water. Fish, plants, and the process of nitrification all have required levels of pH so it is important to have the proper level based on your use. It is normally safe to operate the systems with a pH level of 7.
When introducing chemicals into an Aquaponics system, it is important to verify that the type and amount of the chemicals will not harm the fish. Calcium hydroxide and potassium hydroxide are used in Aquaponics systems to raise pH. If the pH level is too high, that means that too much was added to raise the pH or that the water is hard. The nitrification process, which mainly grows the plants naturally, lowers the pH level. If the hardness is too high, it might take your system longer to start producing plants. This can be avoided by ensuring proper water quality when you start.
Hardness (KH)
There are two types of hardness measurements. Most of us are familiar with general hardness which is mainly the measurement of calcium and magnesium ions in the water. In Hydroponics most plants will need a very small amount of calcium and magnesium ions but these can be provided in the Hydroponic Nutrients. A Suitable Water Type will have the calcium and magnesium ions removed.
For our purposes, we will explain the carbonate hardness (KH). KH is mainly the water's capability ("buffering capacity") to adjust the pH level and it is measured in dH (degree hardness). This value usually is not important unless you are using a non preferred water source or are having some issues in your hydroponic system.
The KH level measurement can become important if you are trying to change your pH level. If the KH level is 4.5 dH or lower, it will be easier to change the pH level by adding a suitable acid to the water. Higher levels of KH could take more acid to lower the pH level, but this will also lower the KH level creating the possibility of the pH dropping lower than expected. Higher KH levels are beneficial when systems are at an optimal condition in the case you do not want the pH level to change much.
The KH level can be measured by use of a simple KH test you can find at the local pet shop or pool supplies store.
Temperature
The temperature has an effect on many variables in the quality of water. Fish, plants, and the process of nitrification all have unique required temperature ranges making it important to have the proper temperature based on your use.
In Hydroponics a water temperature of 70°F is usually safe but can differ based on the types of plants you grow.
Solids
In Hydroponics solids are usually not an issue if you use a Suitable Water Type or any other water type that is safe to drink.
In Aquaponics, solids could be created by fish waste and/or uneaten fish food. This would normally require a bio filter (biofilter) if used on a large system but can be fixed by maintenance on the pump and pump bag. The pump will catch the majority of solids in the filter and the pump bag openings can capture some as well.