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Basics of Building-Your-Own Hydroponic Garden

Building a hydroponic garden can be simple if you understand a few basics and have a creative attitude.

Included on these pages are plans for 3 different types of hydroponic garden 1) a Wick System, 2) an Aquarium System, and 3) a Gravel System. They are listed here in order of complexity and time to build even though the most productive and ultimately the most satisfying, in my opinion, is the Gravel System. If you are new to hydroponics you may want the get your feet wet with a Wick System or an Aquarium System. Once you get the idea you can graduate to a gravel system. Try to keep it simple.

Almost every hydroponic garden starts with the same four parts, 1) a grow bed, 2) nutrient reservoir, 3) grow media and 4) nutrient solution. It sounds simple, but the first two usually cause the most agony for many new gardeners. You probably will ask yourself, "Where should I start - build from scratch (too complicated for many), buy an existing manufactured garden (may be too expensive for the budget), or use ordinary gardening creativity with existing materials, modified to meet the basic requirements." I prefer the latter see Creative Component Sources - Do-It-Yourself.

GROW BED CONTAINER – The grow bed is elevated above the nutrient reservoir to use gravity flow during a nutrient cycle. When the grow bed is full of nutrient and grow media, it is quite heavy and needs to be sturdy, waterproof and well supported. Avoid metal unless it is coated. Plastic works best. It should be six to ten inches deep depending on the system used. You may have to drill a few holes in it so it should not be too hard or thick.

NUTRIENT RESERVOIR – The nutrient reservoir is positioned below the grow bed to use gravity to return the nutrient solution after feeding. It can be as deep as you want but must have at least the same volume as the grow bed. Plastic is the preferred material. If you plan to set the grow bed on top, be sure the sides are sturdy enough to hold the weight.

GROW MEDIA – Be sure the media is chemically inert, without any decaying organic materials. There are ways to interject organic nutrients, but not through the media. Some media choices are: rockwool; sand; vermiculite (manufactured from mica – high water retention and capillary action); perlite (light weight substitute for gravel or mixed with vermiculite for less capillary action); peat moss (partly decayed organic matter but may be used in hydroponics since it decays very slowly – retains 10 times its weight in water); construction grade pea gravel (drains well but may have detrimental impurities and harmful chemicals – should be sterilized and leached with dilute acid solution); expanded clay i.e. Hydroton. It is the best as is for gravel culture with no modification.

More about media can be found in my published works, "Everything You Need to Know Growing Vegetables Without Soil."

NUTRIENT SOLUTION – an in-depth and detailed evaluation of hydroponic nutrient solutions is beyond the scope of these plans. But, in general, you should use a hydroponic nutrient, either dry or liquid, that includes all the necessary trace elements. These are available on-line at Gardening Community Products at Discount Prices.

A slightly acid solution is desirable in order that the plants will absorb the right amounts of the nutrients needed. A recommended average pH is 6.4 (7 is neutral). An inexpensive pH test kit will do. Usually you will be required to add acid to the solution to balance the pH. Use dilute sulfuric or phosphoric acid. Do not use pool acid unless it is dilute sulfuric acid.

Much more can be found regarding nutrients, deficiencies, pH factors, etc. in "Everything You Need to Know Growing Vegetables Without Soil."

Plans - Wick System

The Wick System is the simplest and easiest to build of all the systems available. It is also passive, with no moving parts. It requires no electrical energy source or special attention.

The nutrient solution is drawn into the grow bed from the nutrient reservoir through the capillary action of wick material and absorbent grow media.

There are three minor concerns:

When plants get very large, they may use nutrients faster than the wicks can supply them.
Unused nutrients in the form of salts tend to accumulate, requiring periodic flushing of the grow bed with water or slightly acidic solution.
Aeration or getting oxygen to the roots is difficult since the media holds moisture. To solve the problem put a 2 inch layer of gravel or Styrofoam in the bottom of the grow bed or, add an air pump and an air stone in the nutrient reservoir to help aerate the solution. (See below under Water Culture.)

Building Your Own Wick System

There are numerous examples of existing materials for use as a grow bed and nutrient reservoir.

Paint Buckets - For the easiest and quickest method, use two 2 gal. opaque paint buckets. Nest one inside the other with the bottom being the nutrient reservoir and the nested top bucket the grow bed. To provide more room for the nutrient solution, place an upside down 6 inch pot in the bottom of the reservoir for the grow bed bucket to rest on.

Wick – It is important to use a wick material that is highly absorbent, i.e. braided polyurethane yarn or fibrous rope. Do not use nylon (does not absorb) or cotton (rots easily). Before using it, wash the wick material with detergent to improve the capillary drawing ability.

Drill at least 4 holes in the bottom of the grow bed just large enough to accommodate the wick material. Loop 2 long strands of wick up through the bottom of the grow bed to the top of the media and back down the remaining 2 holes. See illustration.

Fill Tube – Obtain a 1 inch tube (may use 1 ¼ inch PVC Pipe) long enough to extend from the top of the media to about ½ inch off the bottom of the reservoir. This is used to measure the amount of nutrient in the reservoir and to refill it as necessary. Drill a hole in the bottom of the grow bed and insert the fill tube prior to adding the media. See illustration.

TIP: Use a stick with a small Styrofoam ball attached at the bottom as a measuring device. The ball will float inside the tube providing an instant measurement at a glance.

Grow Media – I usually mix equal parts of peat moss, vermiculite and perlite as the grow media from you local nursery. The consistency and water absorption characteristics seem to work better. Add a two-inch layer of gravel or Styrofoam and extra holes in the bottom for better drainage. Try it before you plant to see if the capillary action works. If not, add either more perlite for less absorption or more vermiculite for more absorption. The top layer should be moist, but not wet.

Aeration – It is not shown in the illustration, but for larger gardens having more than one plant, I recommend that you add an inexpensive air pump, air line, and air stone. See the one shown in the Aquarium System below to aerate the water for more oxygen to the roots.

Nutrient Concentration – Nutrients tend to concentrate in the media over time between flushes. Some crops, like tomatoes, remain planted in one container for several months. In that case flush out the media with fresh water every two to four weeks. For nutrients to purchase see Gardening Community Products at Discount Prices.

Plans - Water Culture

An Aquarium Garden (Water Culture) is easy and inexpensive if you already have the aquarium, air pump, air line and air stone. If you don’t have one, you can substitute the aquarium with any deep plastic container. It would be an advantage if the walls were opaque.

Plants grow with the roots suspended in the nutrient solution. The only grow media needed is to fill small plastic cups. The cups are positioned in a floating platform made from Styrofoam.

The only drawback is that you can’t grow large plants without an extensive plant support system like a trellis, etc. But, it is ideal for lettuce and other small water loving plants.

Building an Aquarium Hydroponic Garden

If you already have an aquarium, air pump, air line and air stone, all you need to add are:

a small sheet of Styrofoam 1 to 1½ inches thick,
Several small 3 oz. plastic cups,
Grow media,
Hydroponic nutrient, and
pH test kit.

Floating Platform – Cut the Styrofoam sheet in a rectangle with the measurements 1 inch less than the inside measurement of the aquarium for both the length and width. This allows for a ½ inch gap between the platform and the side of the aquarium around the entire perimeter. It is needed so the platform will float freely and not bind with the sides of the aquarium.

Drill or cut holes in the platform using the actual diameter of the plastic cup you are using. The size of each hole should be just large enough to let the bottom of the cup protrude through the hole to about ½ inch below the level of the water (bottom of the platform). Don’t make the holes too large, which would let the cups fall through. Space the holes according the crop you are growing. About 5 to 6 inches on center should be enough for ordinary leaf lettuce.

Drill or cut several holes in the bottom of each cup for roots to grow through. They should be about 1/8 to ¼ inch each.

Grow Media – A rockwool cube or similar grow block works great. Or mix ½ perlite and ½ vermiculite and fill each cup with the grow block or mixture. If needed to prevent the mixture from falling through the holes, place a small piece of cloth or plastic screen in the bottom of each cup.

Plants – Plant either seedlings or seeds in each cup. For seeds you should sprinkle water from above on each cup periodically until seeds have germinated and roots are forming.

Nutrient Solution – Fill the aquarium with water. Mix the nutrient according to the label and adjust the pH. NOTE: When the level of the nutrient solution falls, add diluted nutrient as needed. The concentration of nutrient should be reduced to about ½ or ¾ strength each time to allow for nutrient concentration buildup due to evaporation. During especially hot weather, you may want to add water only or, if you can siphon it out you may want to mix a new nutrient solution for the entire reservoir. For nutrients to purchase see Gardening Community Products at Discount Prices.

Sunlight – If direct sunlight is allowed to penetrate through the glass of the aquarium, algae will form and cause a mess. To prevent this from happening, cover or at least shade the aquarium with black opaque plastic film or a similar material. Any method to keep direct light from entering is sufficient.

Finish – Add your platform to the nutrient solution floating on top, set up your air pump, line and air stone in the bottom of the aquarium. See illustration. Good luck.

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