Total-control Indoor Gardening with Modern Hydrop

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Testing

If you are at all unsure of your water's quality, you are best advised to collect rainwater or buy distilled water until yours is tested. Your local Cooperative Extension Service or Farm Coop can steer you to a nearby testing lab. or you can send off for a kit. For about $150, you'll get a comprehensive test (at that price, it had better be comprehensive) for germs, parasites, and the whole array of heavy metal and chemical contaminants.

If your water is unsuitable for hydroponics, you may not want it for drinking. A reverse osmosis water purification machine or small "still" will get rid of every problem and is less expensive, in die long run, than buying water.

With even test-proven pure water, you must make (and keep) it chemically neutral—with a reading between 5.0 and 7.0 on the 01 (strong acid) to 14 (strong alkali) pH scale. To start, a soil test or aquarium test kit will do. You must have filled little tubes with aquarium water, added a drop of bromethyl blue, and compared the color to a chart ... then mixed in sodium bicarb to neutralize acid and raise pH or add vinegar or aspirin (acetosalysilic acid) or another acidic powder to raise the acid and lower the pH in a fish tank.

Hydroponics kits work on the same principle, but are more sophisticated. Professional "pH Up" (potassium hydroxide) and "pH Down" (phosphoric acid) come in semiconcentrated liquid form, can be measured precisely, and work instantly. Both are plant foods and will be used by your plantings. But out of the bottle, they are moderately caustic and must be kept in a child and pet-safe location and used with care.

Common white vinegar and bicarbonate of soda baking powder will do the job and are cheaper and more benign but harder to use.

The less expensive meters have a pair of metal probes that are dipped in a water sample for readings. You must clean them with rubbing alcohol, then calibrate them using a solution of a given strength that is supplied with the meters, along with instructions that we won't repeat here. The pH readings are straightforward. You calibrate for neutral: pH of 7.0. For most plants, you use the "Up" and "Down" solutions to keep pH between 6.3 to 6.5. Don't be adjusting pH at every tiny change. It fluctuates naturally and the "Up" and "Down" fluids add their own salts to the water.

PPM is a little more complicated than pH. It is a measure of the amount of dissolved salts in the water; the more concentrated the salts, the more current will flow between probes, and the higher the EC/PPM reading. With young water (less than a week old) you use the readings to tell when plants have consumed enough food and you need to add more nutrient. As water ages, the readings tell you that it is becoming saturated with salts and it's getting near time to replace it. Temperature of the test water can affect readings. When you get a PPM/EC meter, follow the instructions carefully.

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