Introduction: How to Create a Miniature Tomato Hydroponic Rig

Hydroponics is the cultivation of plants by placing the roots in liquid nutrient solutions rather than in soil. The process may sound strange at first, but a brief look at the history of the Aztecs will indicate that this horticulture strategy has been in use for thousands of years. Driven from their land, the Aztecs were forced to grow their crops by building rafts that floated on top of the lake allowing the plants roots to dangle into the water. With this technique the Aztecs were able to harness the nutrient filled water of the lake and grow enough food to become a mighty civilization.

Why Hydroponics?
Growing hydroponically offers many benefits over the standard soil grow as it eliminates all pests and bacteria associated with a normal soil grow that can hurt your crops. Along with less potential dangers, hydroponics allows the plant to grow larger as standard soil grown plants focus a lot of energy on spreading its roots throughout the soil in order to properly absorb nutrients. As hydroponically grown plants have their roots dipped directly into a nutrient rich liquid solution root growth is a very small concern to the plant which allows them to focus all their resources on fruit growth, which is what everyone cares about anyways.

Step 1: Preparation


The following instructable will allow users to create a cheap miniature tomato growing hydroponic rig. The total time to create this small rig is about 15 minutes. Once created, the hydroponic system can be used in any indoor room and offers the room an artistic display of creativity.

Materials needed
All of these materials can be bought from a common hydroponics store which many major cities will have several of. All the materials together should cost no more than $15 together as this is a small set up.

• Bottle of nutrients (Can be obtained for free at a hydroponic store, just ask for sample nutrients)
• Rockwool cube (The medium the seed will be directly placed into)
• Hydroton (Brown Rocks that will hold the roots of the plant stable)
• 2-inch net cup (cup that will hold both the hydroton and rockwool cube)
• Air pump (can be purchased at Wal-Mart for $6.50)
• Air pump tube (Wal-Mart for $1.50)
• Tomato Seeds (Wal-Mart for $3)
• Air stone (Wal-Mart for $1)
• Small soda bottle (any size will work as long as top near lid is narrow)
• Distilled water (Important! Needs to be chlorine free.)
•pH testing strips(optional)
The hydroton, rockwool cube, and net cub were all purchased from ebay for $6.00 here:

Scissors or Knife
Bowl or Cup

Caution: You will be using a knife or a pair of scissors, be careful as not to point the knife or scissors at yourself as you may cut yourself if you are not careful.

Step 2: How to Create a Minature Hydroponic System

Empty and clean a small soda bottle with hot water to sanitize and eliminate any bacteria left behind in the bottle.  Smaller water bottles are desired over larger soda bottles as they have a lower center of mass and are less likely to tip over causing a mess you don’t want to deal with.

Step 3:

Cut the top of the water bottle of as seen in the figure below.  Make sure to cut a circle in the top of the water bottle to have a diameter of 1.5 inches as you will place a the net cup into it.  Start with attempting to make a smaller circle as it is always possible to take away plastic but you will not be able to add plastic back after the cut.

Step 4:

Place the net cup into the bottle and make sure it fits snug. Try to have it sit level and comfortable as you don’t want it to either pop out or fall into the bottle. Once your comfortable with how it fits take off the net cup for the next steps.

Step 5:

Add distilled water into the bottle just half an inch from the bottom of the net cup.  If you do not have access to distilled water and want to use tap water make sure to let the water sit in the bottle for 6 hours. This way the unstable chlorine in the tap water is allowed to evaporate which is desirable as chlorine is poison to plant life.

Caution: The next step will involve the use of hydroponic nutrients, common to fertilizer this ingredient is not meant to be ingested by humans. Please do not drink your nutrients as it may bring fatal consequences.

Step 6:

Add a very small amount of nutrients to your cup as seedlings need little nutrients compared to full grown plants.  Use the corresponding directions on the label of your nutrients to determine the amount to add. (For technical writing: add a tablespoon of the blue nutrients, or a spoon full if you do not have measuring supplies.)

Hint: It is important to make sure the water has an appropriate pH level for the stage and type of plant you are growing. For tomatoes the optimum pH range is 5.5-7.5.  You can use Epsom salt to try to neutralize you pH level.
(If you are unfamiliar with what pH is check out this link:  )

Professional Tip: If you are using a utilizing a reservoir for multiple plants or want better results look into buying an electronic pH meter as most of them also tell you the ppm (parts per million) and temperature of your water (around 68 degrees fahrenheit for tomatoes).  The price tag associated with this technology is usually in the $250 range however.

Step 7:

Set up the air pump.  Cut at least 2 feet of air tubing and plug one end of the air tube into the air pump.  You want to have enough slack with the air pump so it does not tip the bottle over.  Then thread the other end of the air pump through the net cup and add an air stone to the end.  Then proceed to let the air stone sit in the bottom of the water.

Step 8:

Soak your Rockwool cube in distilled water and make sure to squeeze out excess water.  It is important that the cube is neither too wet nor too dry for the seedling to root properly.  Squeeze the cube firmly until it no longer drips any water to ensure the cube is damp.

Step 9:

Add the seed to the cube and rip of part of the Rockwool cube and place it over the seed as to protect it from light.  This will give the seed the impression it is underground and will put it into a germination phase.

Step 10:

Put the one level of small brown rocks called Hydroton into the bottom of the net cup so that the Rockwool cube is not directly touching the bottom of the net cup.  Then proceed to surround the Rockwool cube evenly with more Hydroton rocks.  These Hydroton rocks will give the roots that sprout from the Rockwool cube a firm grip so that the plant can hold itself up before its roots venture into the water.

Step 11:

Finally the last step, plug the air pump into the wall outlet. Bubbles should flow from the bottom of the cup and very lightly keep the bottom of the net cup moist, this way the roots of the tomatoes plant grow downwards into the cup and dunk themselves into the water.  It is important to have the air bubbles on most of the day as, the air bubbles not only hydrate the plant they mix the nutrients up in the bottle as well as provide the very necessary oxygen plants need. 

Lighting: It is also important to note that tomatoes perfer a light cycle of 18 hours on and 6 hours off.  Light from incandecient light bulbs and CFLs are usually not sufficent enough for plant growth so it is important that you have your rig near sunlight. 

Nutrients: Change the resivoirs water weekly and make sure to not use tap water!  Once the tomatoe starts to sprout you can slowly increase your nutrient dosage by 10% a week until maturity.

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