Unlike plants in soil, the roots of hydroponic plants are provided with water, oxygen and nutrients through one of several hydroponics systems. The big challenge is to make certain the nutrient solution is keeping up with your plant needs. At the same time, it's necessary to avoid excesses or deficiencies of minerals, extremes in pH, temperature or a lack of oxygen.
Don't take your water for granted
Because your nutrient solution is made up mostly of water, the quality of your water is important. If you're using well water or water from any other source, you have to check it regularly with a dissolved solids meter (PPM).
After testing, you may find your water contains high levels of salts like Calcium and Magnesium carbonates these are among the most common minerals found in excessive amounts.
Generally, a calcium content of more than 200 PPM or 75 PPM of magnesium can be on the edge of excessive. This can create a situation called ‘lock-out’. When lock-out occurs, other important elements or minerals can become unavailable to your plants.
If you find your water is hard or contaminated with excessive amounts of any element, your best recourse may be a water purification system. One of the best is a system called ‘RO (reverse osmosis’.
Watch that temperature
Your plants generally will appreciate root zone temperatures between 65 degrees (18 C) and 80 degrees (27 C). The solution can be a little cooler for winter crops and a little warmer for tropical plants.
If your solution is too cold, seeds won't germinate, cuttings won't root and plants will tend to grow more slowly. In some instances your plants will stop growing altogether and die. The same applies if you allow the root mass to become too hot.
Also keep in mind that plants don't like rapid changes in temperatures, particularly in the root zone. So, when adding water to your reservoir, the best practice is to let it sit long enough to reach the same temperature as the water in the reservoir.
Keeping watch over the pH
The best way to control pH is to mix fresh hydroponic nutrients with your water and let it stand to stabilize the pH. After it is stabilized, you can add products to increase or lower the pH.
Most plants prefer a pH that's between 5.8 and 6.3. Keep in mind that it's common for pH to drift up for a while, then down, then back up again. You can safely allow this drift to range between 5.5 and 7.0 without adjusting it. In fact, it's better for your plants if you don't keep dumping a lot of chemicals into your solution to try and maintain a perfect 5.8 to 6.3.
When to change your nutrient solution
- When you start out with a fresh solution in your reservoir, note the date, pH and EC or PPM.
- When the reservoir level drops, note the EC/PPM level and top it off with fresh water.
- Retest the EC/PPM. If the nutrient strength has dropped significantly, add a bit more nutrient.
- Always record how much water you add to top-off your reservoir. When the total amount of water you've added equals the capacity of your reservoir, it's time to drain and replace all of your nutrient solution.
Beware of disease in your solution
Perhaps one of the most important things you can do to keep your grow room disease free is keep it clean. Be particularly careful about allowing soil to be accidently kicked or dropped into your solution. If this happens, all your hard work could end up for nothing.
If you see evidence of disease in any single plant, get rid of it immediately. Then keep a close watch on your other plants and destroy any that show the same symptoms. Then completely drain and renew your nutrient solution. If possible, flush your entire system by running fresh water through it without any nutrients. It's better to lose a few plants than your entire harvest.