Water and Hydroponics

One of the most important elements to hydroponics is maintaining a good nutrient solution for the particular plant you are growing. Your nutrient solution needs to:

• Have have the necessary micro and macro nutrients to provide everything that your plants roots need. Plants need 16 chemical elements for successful growth. 3 of these come from the air and water around the plant, Carbon, Oxygen and Hydrogen. There are 6 macro nutrients in the fertilisers we need to add to the water. Nitrogen, Phosphorous, Potassium, Calcium, Magnesium and Sulphur. These are the key elements we need to add. There are then 7 further micro nutrients necessary for healthy plants. These are only required in very small amounts and include, Copper, Zinc, Boron, Molybdenum, Iron, Manganese and Chlorine. By managing these nutrients in the right concentration for the right stage of growth and you will have happy plants.

• Be the correct concentration. Your plants will require enough nutrients in the water so they have all they need but not too much as that can damage them. Different plans require different concentrations of nutrients to grow their best. The best means of establishing the nutrient concentration level is with an Electrical Conductivity (EC) meter. An EC meter measures how easily electricity can pass through the liquid. The more electricity it conducts the more nutrient (ion) are in the water. Lettuce for example needs an EC level of between 0.8 and 1.2.

• Be kept at a suitable pH for your plants. pH is a measure of how acid or alkali the water is. The pH of the solution determines whether the plants roots are able to access all the nutrients it needs. Different macro and micro nutrients have an optimum pH for your plants to access them. Therefore a balance is required, not too acidic and not too alkali. Usually maintaining a pH of between 5.8 and 6.2 is suitable.

• Have a suitable temperature. Your plants roots will go into shock if the temperature changes dramatically. Therefore ensure that your water temperature for your nutrient is close to the ambient temperature.

• Oxygenated. Your plant roots require access to oxygen dissolved in the water. Stagnant, de-oxygenated water is bad for root health. We can overcome this by aerating the water with air stones, moving the water around with pumps or even spraying the nutrient onto the roots as in aeroponics. In smaller volumes of nutrients where a sufficiently large surface area to volume is maintained, the water will remain oxygenated without these aids, greatly simplifying the set up and eliminating the need for electricity.

Mixing Hydrofeed Complete nutrients and pH adjust - what water to use?

The water you use to create your nutrients can be very important however it doesn’t necessarily have to be perfect. Not all water is the same! Water will normally contain impurities such as dissolved minerals. You can test how pure your water is with an Electrical Conductivity (EC) meter. If the meter reads 0 then the water is pretty pure. In Hydroponics, pure water is often cited as being required since it allows the gardener to add only those minerals that they wish for their plants. Starting with pure water means that you will know exactly what is in the water once you’ve mixed up your nutrient. We’ll explore differ water options below:

• Tap Water - Water from your tap will have been treated in order to kill any harmful parasites, bacteria and viruses. Depending upon where the water is sourced from it may also have some or a lot of dissolved minerals. Often referred to hardness. These minerals can be used by your plants however it is not easy to know what minerals are in the water and at what concentrations. You may find that the measured EC of tap water could be 0.2 to 0.8 or more. Some plants like lettuce and seedlings don’t thrive when the EC is too high, for example lettuce prefer an EC of 0.8 to 1.2. If the tap water is contributing 0.6 of that EC for example then there’s only room for 0.6 EC or so of nutrient before the nutrient will be too strong for your lettuce. This is another reason why it is preferable to start with pure water. Your plants will have access to the best concentration of nutrient. For home gardeners however, you can get good results growing with most tap waters and raising the EC to the required level for the plant you are growing. If the EC of your tap water is too high then there are other options.

• Rain Water - Collected rainwater can be a good source of water for Hydroponics. The dissolved mineral content will be much lower and it reduced the demand on our drinking water. The pH will often be more acidic than tap water so it may need the pH raising with pH UP once you’ve added your nutrients (nutrients tend to lower the pH of water). It will be important to remove any organic matter from the rainwater as this will reduce the dissolved oxygen at it starts to decompose.

• De-ionised / Distilled Water - Pure de-ionised water with an EC of 0 can be purchased from most supermarkets and garages. It is used for car radiators and in clothes irons. It will be a rather expensive option particularly if you are growing any quantity of plants however.

• Mineral Water - A cheaper alternative to de-ionised water is mineral water which you can buy in bulk at any supermarket. Despite it’s name most bottles of mineral water found in the supermarket will have a lower mineral concentration with an EC about 0.2 to 0.4. This can be used successfully for Hydroponics growing.

• Reverse Osmosis Water - It is possible to remove the dissolved minerals from water through a process called reverse osmosis. This is the approach that commercial growers or enthusiasts will use but does require some expensive equipment. When growing large quantities of plants with hydroponics, this is the most economical approach to controlling the EC of the water prior to adding nutrients.

As you can see there are many options, each with their own advantages and disadvantages. We would recommend trying a few and seeing which works best for you. Unless your tap water is particularly hard, for small scale growers, this is likely to be the easiest option to take.