The nutrient solution is pretty much the deciding factor for the success of your hydroponic garden. Get this right and your garden will be robust and produce ample quantities of fresh juicy veggies for you. Get it wrong and you will waste your time and money, but rest assured, it doesn't take a degree in chemistry to do this. Heck, you could even buy your nutrients in a ready to use liquid concentrate form.
There are basically 4 components to this:
Good water - When it comes to hydroponics, basically what you should be concerned about is the calcium content of the water. You know you have a high calcium content if you notice a white crusty residue around your faucets. Water that has a high calcium content is otherwise known as "hard water". Soft water is preferable to hard water, but having hard water doesn't preclude having a hydroponic garden. If you are going to use softened water from a tap, you shouldn't use water that has been ran through a water softener as it will be way to salty. The ideal water to use would be rain water collected in a barrel.
Macro & micro nutrients - Plants need all of 6 macro-nutrients to thrive and survive. The main 3 macro-nutrients that plants need are Nitrogen (N), Phosporus (P), Potassium (K). The ratio of these elements is typically printed on the packaging of the fertilizer that you purchase and is represented by three numbers like 15-25-10 or something like that. The numbers represent the amount of each elemental nutrient by weight that is immediately available to the plants. For instance a 100 pound bag of 15-25-10 fertilizer would have 15 lbs. of nitrate (N), 25 lbs.of phosphate (P) for the phosphorous, 10 lbs. of potash (K) for potassium, and 55 lbs. of filler. Plants also need 3 more macro-nutrients which are calcium, sulfur, and magnesium. The trace elements (micro-nutrients) that plants need are iron, boron, molybdenum, zinc, manganese, copper, cobalt, chlorine, selenium and silicon. All of these hydroponic nutrients are typically sold in liquid form, but I buy my fertilizer in dry form made specifically for hydroponics and then mix it myself. Its cheaper that way. However, when I first started out I purchased General Hydroponics Flora Series QT - FloraGro, FloraBloom, and FloraMicro.
The first two bottles contain different NPK ratios for different stages in the plants development and the micro-nutrients in the third bottle. This is the same set of hydroponic nutrients that NASA uses in their hydroponic systems so you know you'll be getting the best there is when you click on the link above.
pH - pH is the one factor that can make or break your hydroponic garden. All pH is is a number that tells how acid or alkaline your solution is. This is key, because if the pH is not in the proper range, nutrients get "locked out" and the plant can't get to them. Don't be put off by this factor though because pH levels are easy to control. All you need is a pH test kit (like for swimming pools), or pH "dip" strips. To order the one that I use, click on the link: General Hydroponics GH1514 Ph Control Kit This testing kit is inexpensive (only like $15) and very easy to learn. Don't waste your money on an expensive electronic pH meter.
The ideal range of pH for your nutrient solution: 5.5-6.5 (6.0 is best). The best time to test for proper pH is a few minutes after you add your nutrients to the water (with the pump on) then every three days after that unless something happens such as large quantities of freshwater being added to the reservoir. This may happen if your hydroponic garden is outside and it rains.
Mixing the hydroponic nutrients & maintaining the reservoir - To mix your hydroponic nutrients solution never add the solution directly to the reservoir. Always mix up a batch first then pour it in. This helps to ensure that it is thoroughly mixed and helps to prevent spikes in pH. If you are using chlorinated tap water let your batch of solution sit out outside for a day before you add it to the reservoir. The sun will break down the chlorine.
To maintain your reservoir simply keep the temperature of the water between 60 and 80 degrees and keep it full. Just do not top it off when the pump is running especially if you have a flood and drain system. Otherwise when the nutrient solution drains back into the reservoir it might overflow. Not a problem if your system is outside, but big trouble if its indoors. Also, its a good practice to add a few drops of hydrogen peroxide to your reservoir when you change the water to inhibit the growth of bacteria and algea. It is imperative to also make sure you keep the water well aerated. If you don't then anaerobic bacteria will multiply. You can use any aquarium air pump and large air stone for this. This will not only prevent anaerobic bacteria from building up and creating stagnant water conditions but also it will oxygenate the roots (also necessary).
