Frequently Asked Questions about Hydroponics
in no particular order
What is hydroponics?
In general, hydroponics is a growing method in which the plant's growing medium contains no nutritional value. Everything the plant needs to stay alive including nutrients, micro nutrients , trace elements, carbohydrates, sugars and vitamins are all delivered to the plants through the roots via a nutrient rich solution.
How does hydroponic growing differ from growing in soil?
The key difference that the media contains absolutely no nutritional value for the plant. It is merely to provide ideal textural conditions for roots. Some systems like NFT or aeroponic the roots are just danging in the air, with no medium, and is supported by a plug or basket in the system.
Soil contains a minimal amount of primary secondary and trace elements. Enough for most plant life to sustain itself on all by itself.
In a hydroponics system, all these nutrients and trace elements are provided by water soluble nutrients added to water to make a solution that is used to feed the plants several times daily.
What types of systems are used for hydroponics?
There are several different types of systems which are all very effective in their owns ways, some have some advantages to others while many have their own disadvantages as well.
The Wick System
The Wick system is by far the simplest type of hydroponic system. This is a passive system, which means there are no moving parts. The nutrient solution is drawn into the growing medium from the reservoir with a wick. Free plans for a simple wick system are available.
This system can use a variety of growing medium. Perlite, Vermiculite, Pro-Mix and Coconut Fiber are among the most popular.
The biggest draw back of this system is that plants that are large or use large amounts of water may use up the nutrient solution faster than the wick(s) can supply it.
Water Culture aka DWC aka Bubbleponics
The water culture system is the simplest of all active hydroponic systems. The platform that holds the plants is usually made of Styrofoam and floats directly on the nutrient solution. An air pump supplies air to the air stone that bubbles the nutrient solution and supplies oxygen to the roots of the plants.
Water culture is the system of choice for growing leaf lettuce, which are fast growing water loving plants, making them an ideal choice for this type of hydroponic system. Very few plants other than lettuce will do well in this type of system.
The Ebb & Flow System aka Flood and Drain
The Ebb and Flow system works by temporarily flooding the grow tray with nutrient solution and then draining the solution back into the reservoir. This action is normally done with a submerged pump that is connected to a timer.
When the timer turns the pump on nutrient solution is pumped into the grow tray. When the timer shuts the pump off the nutrient solution flows back into the reservoir. The Timer is set to come on several times a day, depending on the size and type of plants, temperature and humidity and the type of growing medium used.
The Ebb and Flow is a versatile system that can be used with a variety of growing mediums. The entire grow tray can be filled with Grow Rocks, gravel or granular Rockwool. Many people like to use individual pots filled with growing medium, this makes it easier to move plants around or even move them in or out of the system. The main disadvantage of this type of system is that with some types of growing medium (Gravel, Growrocks, Perlite), there is a vulnerability to power outages as well as pump and timer failures. The roots can dry out quickly when the watering cycles are interrupted. This problem can be relieved somewhat by using growing media that retains more water (Rockwool, Vermiculite, or coconut fiber). Drip Recovery aka Top Feed 
Drip systems are probably the most widely used type of hydroponic system in the world. Operation is simple, a timer controls a submersed pump. The timer turns the pump on and nutrient solution is dripped onto the base of each plant by a small drip line. In a Recovery Drip System the excess nutrient solution that runs off is collected back in the reservoir for re-use. The Non-Recovery System does not collect the run off.
A recovery system uses nutrient solution a bit more efficiently, as excess solution is reused, this also allows for the use of a more inexpensive timer because a recovery system doesn't require precise control of the watering cycles. The non-recovery system needs to have a more precise timer so that watering cycles can be adjusted to insure that the plants get enough nutrient solution and the runoff is kept to a minimum.
N.F.T Nutrient Film Technique 
This is the kind of hydroponic system most people think of when they think about hydroponics. N.F.T. systems have a constant flow of nutrient solution so no timer required for the submersible pump. The nutrient solution is pumped into the growing tray (usually a tube) and flows over the roots of the plants, and then drains back into the reservoir.
There is usually no growing medium used other than air, which saves the expense of replacing the growing medium after every crop. Normally the plant is supported in a small plastic basket with the roots dangling into the nutrient solution.
N.F.T. systems are very susceptible to power outages and pump failures. The roots dry out very rapidly when the flow of nutrient solution is interrupted.
AeroPonic 
The aeroponic system is probably the most high-tech type of hydroponic gardening. Like the N.F.T. system above the growing medium is primarily air. The roots hang in the air and are misted with nutrient solution. The mistings are usually done every few minutes. Because the roots are exposed to the air like the N.F.T. system, the roots will dry out rapidly if the misting cycles are interrupted.
A timer controls the nutrient pump much like other types of hydroponic systems, except the aeroponic system needs a short cycle timer that runs the pump for a few seconds every couple of minutes.
How large of a reservoir do i need?
It all depends on the size of your system. If your running an ebb and flow with a basin thats 20 gallons, your reservoir should be atleast 20 gallons. A top feed system wouldnt fill the enitre basin, so you would need less for that, unless you had a large topfeed or NFT system, with several different basins or gullies.
How often should i change the reservoir?
Smaller reservoirs need to be changed more often. A good rule of thumb is every 2 weeks or more, completely empty out and clean your reservoir. The plants will use up different amounts of the nutrients it needs and may end up containing higher levels of certain elements that you may not necessarily want. So to make sure you have the proper balanced nutrient solution... change it every 2 weeks.
What kind of nutrients should i use?
This is a matter of choice, everyone says they use the best nutrients. But what is essential for hydroponic growers. You couldn't just use a household fertilizer like miracle grow, miracle grow is lacking in certain secondary and trace elements that are usually found in soil, but not in a hydroponic medium.
How do i know how much nutrients to use?
Every nutrient system will have dilution ratios on the back, usually a teaspoon per gallon. Most 3 part systems require you to add the first part to the water first, as the first and second part in their concentrated forms conflict chemically and can break down eachother. Always double check your dilution with a TDS or EC meter.
How do i measure the level of nutrients in my reservoir? With a TDS meter measured in PPM. You can also get an idea by the EC.
What does PPM, EC and TDS mean?
PPM stands for parts per million, and is usually referenced to TDS or total dissolved solids. Distilled water contains a very low ppm compared to tap water which contains minerals and chlorine. EC stands for electrical conductivity, and is another way to measure how much nutrients are in your solution.
What does PH have to do with hydroponics?
The ph will determine how acidic or alkaline your reservoir is. The ideal range for hydroponics is around 5.8. At 5.8 it allows for maximum intake of all essential nutrients the plant needs. Too high of a PH and the plant cant take in the most important primary nutrients, too low of a ph and the roots cant absorb the water properly, and will also affect key nutrient uptake.
How do i measure the PH of my Reservoir?
When you are growing hydroponically checking and adjusting pH is a simple matter, it can be a bit more complicated when growing organically or in dirt. There are several ways to check the pH of the nutrient solution in your hydroponic system.
Paper test strips are probably the most inexpensive way to check the pH of the nutrient solution. These paper strips are impregnated with a pH sensitive dye which changes color when dipped into the nutrient solution. The paper strip is then compared to a color chart to determine the pH level of the solution being checked. These test strips are inexpensive, but sometimes they can be hard to read, because the colors differences can be subtle.
Liquid pH test kits are probably the most popular method to check pH for the hobby gardener. These liquid test kits work by adding a few drops of a pH sensitive dye to a small amount of the nutrient solution and then comparing the color of the resulting liquid with a color chart. The liquid kits are a bit more expensive than the paper test strips but they work very well, and are normally easier to "read" than the paper indicator strips.
The Most high-tech way to check pH is to use the digital meters. These meters come in a huge array of sizes and prices. The most popular type of pH meter for the hobby gardener are the digital "pens". These pens are manufactured by several different companies and are very handy and easy to use. You simply dip the electrode into the nutrient solution for a few moments and the pH value is displayed on a LCD display.
The pH meters are very accurate (when properly calibrated) and fast. They need to cared for properly however, or they will quit working. The glass bulb electrode must be kept clean and wet at all times. The pH meters are actually very sensitive volt meters and are susceptible to problems with the electrode.
The pH meters are slightly temperature sensitive. Many of the pH meters on the market have Automatic Temperature Compensation (ATC), which corrects the reading with respect to temperature. On meters without ATC the pH should be checked at the same time of day each time in order to minimize any temperature related fluctuations.
The pH meters usually need to be calibrated frequently, as the meters can "drift" and to insure accuracy you must check calibration often. The tip needs to be stored in a electrode storage solution or in a buffer solution. The tip should never be allowed to dry out.
Due to the fact that pH meters have a reputation of breaking down without warning it is a good idea to keep an emergency back up for checking pH (paper test strips or a liquid pH test kit), just in case.
How do i adjust the levels of the PH in my reservoir?
There are several chemicals used by the hobby gardener to adjust pH. The most popular are probably phosphoric acid (to lower pH), and potassium hydroxide (to raise pH). Both of these chemicals are relatively safe, although they can cause burns and should never come in contact with the eyes. Most hydroponic supply stores sell pH adjusters that are diluted to a level that is reasonably safe and easy to use. Concentrated adjusters can cause large pH changes and can make adjusting the pH very frustrating.
Several other chemicals can be used to adjust the pH of hydroponic nutrient solutions. Nitric acid and sulfuric acid can be used to lower pH but are much more dangerous than phosphoric acid. Food grade citric acid is sometimes used in organic gardening to lower pH.
Always add the nutrients to the water before checking and adjusting the pH of your nutrient solution. The fertilizer will usually lower the pH of the water due to it's chemical make up. After adding nutrient and mixing the solution, check the pH using what ever means you have. If the pH needs to be adjusted add the appropriate adjuster. Use small amounts of pH adjuster until you get familiar with the process. Recheck the pH and repeat the above steps until the pH level is where you want it to be.
The pH of the nutrient solution will have a tendency to go up as the plants use the nutrients. As a result the pH needs to be checked periodically (and adjusted if necessary). To start out I suggest that you check pH on a daily basis. Each system will change pH at a different rate depending on a variety of factors. The type of growing medium used, the weather, kind of plants and even the age of the plants all effect the pH variations.
How Often should the pump be switched on to water? and for how long?
It depends on the kind of system and medium. A medium like rockwool, oasis foam or coconut fibers need to be watered less often in general. While media like LECA, Stone, or just thin air (dangling roots in aeroponic or nft) need to be watered more often or even constantly. A top feed system can be run 24-7 as long as its a slow steady drip. But in general 3-5 times a day in a top feed, ebb and flow. About once an hour for aeroponic setups or NFT setups as they dry out much faster. When the pump is switched on, it only needs to be on for 15 minutes or possibly longer if your flood and drain system takes a while to fill up.
What kind of daily maintenance is involved in
a hydroponics system?
Your going to want to top off your system between changing with a premixed solution, i add a gallon at a time.
You want to test the pumps and timers to make sure they are all working properly.
You also want to check for any possible leaks on a regular basis. Especially when dealing with homemade setups.
Check the PH and TDS constantly with accurate meters, the plants will take in more water or more nutrients sometimes, so you want to make sure your reservoir parameters remain constant.
What different types of mediums can i use?
There are several different types of mediums used by hydroponic growers. Some work better in other systems as stated above. But some of the more popular mediums...
Grodan rockwool cubes
Great at retaining water, and great at oxygenating roots upon drying out.
LECA aka Clay Pellets
Not as good at water retention, but are reusable.
Oasis Foam
Similar qualities to rockwool
Dyna-Rok II - thanks fredfarted
non-toxic and environmentally safe growing medium suitable for all indoor and outdoor plants, including orchids, roses, annuals, perennials, shrubs, vegetables, and trees. This lightweight porous mineral is super absorbent, taking up as much as 150% of its weight in water and nutrients, which are then slow released back to the plant's roots. Unlike traditional bark mixes, dynarok II will not decompose leading to root rot problems.
This material is a sedimentary rock consisting of the fossilized remains of unicellular fresh water plants known as diatoms. It consists of approximately 90% amorphous silicate with the balance made up of other mineral elements needed for plant growth. Though largely inert, overtime, some silicon and other minerals are released slowly to the plants. This results in faster growth, earlier and more prolific flowering, stronger roots, and improved resistance to pests and environmental stress.
Coconut husk fibers
Good water retention, a bit messy
Pond Rocks
Reusable, provide sturdy support, a bit heavy.
Perlite
The biggest drawback to perlite is that it doesn't retain water well which means that it will dry out quickly between waterings and is non reusable.
Sphagnum Peat Moss
Can retain a lot of water, maybe too much, and is a bit messy.
Sand
Can pack too tightly together, but can be used in combination with other media.
Lava Rocks
Lava rock has been used successfully for years, it is light-weight and retains a fair amount of water in it's holes and pores. It is used most often in ebb & flow (fill & drain) systems with frequent watering cycles.
Among others...
Where can i find plans to make my own system?
In the DIY section of Greenpassion.org
Ebb & Flow
http://www.greenpassion.org/diy/3259...cs-system.html
DWC
http://www.greenpassion.org/diy/2830...ld-1plant.html
Top Feed
http://www.greenpassion.org/diy/3244...cs-system.html
Bucket Water Farm
http://www.greenpassion.org/diy/454-...rm-system.html Hydroponic Myths: -Hydroponics is a new technology.
The Pharaohs of Ancient Egypt enjoyed fruits and vegetables grown hydroponically. One of the Seven Wonders of the World, The Hanging Gardens, was probably a hydroponic garden. If hydroponics is a "new" technology, it is a new technology in general use for thousands of years. Hydroponics is not new -- just different.
-Hydroponics is unnatural or artificial.
Plant growth is a real and natural happening. Plants require basic, natural things for normal growth. Simply, hydroponics supplies the plant with what it needs,when it needs it. There is no genetic mutation that takes place inside the equipment nor are there any mysterious wonder chemicals introduced to the plants roots that tricks them into thinking they're on steroids.
-Hydroponics is bad for the environment.
This is totally false. growing plants hydroponically is far more "earth friendly" than conventional gardening could ever be. Hydroponic's usage of water is 70 to90 percent
LESS then that used in conventional dirt gardening, and no fertilizer is lost to rain run off. These two items alone, water conservation and the non-pollution of lakes and streams, are major plus values.
-The use of hydroponics is not widespread.
Wrong again. Hydroponics is used extensively the world around and for various reasons. It is used in countries where the climate prohibits or limits growth, where the soil is to poor to support large-scale crop production and in countries where once fertile soil has been abused and is now depleted. In British Columbia, 90 % of all the greenhouse industry is now hydroponic. This, unfortunately, leads to yet another, more popular myth.
-Hydroponics must be used indoors.
Hydroponics is as easy to use outdoors under the sun as it is indoors. The advantage to gardening indoors under grow lights is that you, not Mother Nature, control the seasons. Making the growing season twelve months long. However replacing the sun is a relatively expensive proposition.
-Hydroponics requires no pesticides.
This is one myth that we wish were true. It is partially true, because a strong healthy plant is much less susceptible to attack than a weaker plant. This reduces the need for toxic pesticides to control pests. We use and strongly recommend the use of good organic pest controls (such as the Safer's brand of safe, biodegradable, environmentally safe products).
-Hydroponics produces super huge plants.
This is another myth we wish were true. Hydroponics produces superior plant growth, hence, superior yields. Every seed, seedling and plants has a genetic ability to grow at a certain rate,to yield a certain amount of crop and for that crop to taste a certain way. All of these characteristics are controlled by the plants genetic make-up and there isn't anything anyone can do that will make the plant exceed its natural, genetic limits.
Getting a plant to grow to its full potential in common soil is difficult because of the hundreds of variables in the soil's make-up that influence the plant and its growth. It is the ability to control these variables that makes hydroponics superior to conventional gardening. You have full control over what the plant has available to it rather than guessing what the soil can provide. Because of this the plants can do their best.
Dr. Howard M. Resh, in his book HYDROPONIC FOOD PRODUCTION, cites vegetable yield increases that are dramatic; identical cucumber plants produced 7,000 pounds per acre in soil but 28,000 pounds per acre when grown hydroponically and tomato yields that ranged from 5 to 10 tons per acre in soil but 60 to 300 tons per hydroponic acre. The reported results are typical for practically any plant. Said another way, to produce the total number of tomatoes consumed annually in Canada (400 million pounds) requires 25,000 acres of soil. Hydroponically, it would require only 1,300 acres.
....................some questions answered!!!!!! Hope it helps someone!!!!!