The ideal range is different for different plants, but the general range for plant survival is between 5.0 and 7.5. Any lower and delicate plant tissues can be burned and any higher may cause some nutrients to precipitate out of solution, making them unavailable for uptake. It is also important to take into the considration the fact the different nutrients can only be absorbed at certain pH levels. The optimum pH range seems to be between 5.8 and 6.5. .

Ideally, the pH should be maintained at 6.0 as at this point, a drift of half a pH point down to 5.5 or up to 6.5 is entirely acceptable. It will fluctuate (see 14 and 15), so maintaining the pH between 5 and 6.8 is fine. A short time a bit outside of this range should not cause any real problems but try to keep it within the recommended levels as much as possible.

For seedlings, your nutrient level should be between 400ppm (800ms) and 600ppm (1,200ms). For vegetative growth, the level should be between 800ppm (1,600ms) and 1,100ppm (2,200ms). For bloom, the level should be between 1,000 ppm (2,000ms) and 1,400ppm (2,800ms). These of course are very general levels. For exact nutrient requirements for a variety of plants, click here.

pH is a measure of the relative concentrations of the H+ and OH- ions in the root environment .... having said that, it may be best to think of pH as an electrical measurement. Simply put, if the ionic charge is not correct .... the charged nutrient molecules are not accepted for use by the plant, i.e. they are 'locked up'. All plants have very specific pH requirements for the proper uptake of nutrients through their root systems.

It is well known that the body fluids of healthy people tend to be more alkaline (high pH) and the body fluids of sick or diseased people are acidic ( low pH). Healthy blood, spinal fluid and saliva are normally at a pH of 7.4. This alkaline state is necessary for cell growth, cell function and cell repair. It has been proven that cancer cannot grow in an alkaline solution because an alkaline solution will hold oxygen at a high level (Cause and Prevention of Cancer, Biochem Zeits, 152: 514-520).

Ron, I have just discovered your site, and I am finding it very useful, I am a bit of a back yard inventor and I have an idea for building a hydroponic setup using styro-foam can you tell me if there is any problem with this material being used in hydroponics, If not I would like to build a proto type and try it out, Thanks and keep up the good work, Thanks Chris Yes you can use Styrofoam packing peanuts also known as ghost turds or just about any inert porous material that can hold oxygen.

You should keep the nutrient solution temperature in the range of 65 to 80 degrees Fahrenheit (18 to 26 degrees Celsius) with the optimal range between 65 and 75 degrees F. But remember, plants don't like rapid temperature change, especially in the root zone. So before adding water to your reservoir, we suggest you allow it to come to the same temperature as the water in the reservoir.

A good rule of thumb is to always top off your reservoir with fresh water without any nutrient added. You will lose some water through evaporation and plant uptake, but the strength of the solution doesn't necessarily drop the with the level of the solution. Sometimes, as the reservoir water level drops the nutrient solution can actually become more concentrated. To avoid overdoing your nutrient, add only fresh water and then adjust your pH accordingly.

When the plants are young, every two weeks should suffice. With small nutrient tanks you may want to do it more often. When the plants are bigger, (eating and drinking more) it's best to change the solution every week to ensure optimum results.

pH is a measure of the acidity ("sourness") or alkalinity ("sweetness") of soil. The scale ranges from 1 to 14, but few soils are more acidic that 5 or more alkaline than 9. A pH of 7 is perfectly neutral, but most plants grow best when the pH is a slightly acidic between 6.5. Soils in areas with low rainfall tend to be alkaline. Where rainfall is high, soils are more often acidic. This happens because rainfall gradually washes calcium from soil.

You should check your nutrient solution’s reservoir level, conductivity (see 8) and pH (see 13) at least every second day given that you have an adequate reservoir (see 17.) as long as you’re not running high temperatures and you have good water. The more often the nutrient solution is checked the better the chances of preventing serious problems.

To answer this accurately depends on too many variables such as temperature, humidity, medium used, preferred E.C., water source, lighting and plant size to name a few. Most pre-made kits have been designed to water plants correctly, so you would only need to work this out if you were designing your own. Basically, the requirement is to keep the roots moist and aerated all the time but do not over water them as this will deprive the roots of oxygen. For more information please see your retailer.

In Europe, EC has been used exclusively. In the US, most growers have been using TDS. The problem is that, as explained earlier, TDS is a conversion from EC, and different manufacturers use different conversion rates. Different TDS meters may show a discrepancy of as much as 600 ppm when reading the same solution. Last June at the Hydroponic Merchants' Association conference is was decided that the industry will begin to switch over to EC. This switch over could take years.