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A Crash Course in Hydro, Part 1: Passive Hydroponic Systems

Containers in a reservoir tray. An air bubbler helps keep the water oxygenated. The tray was filled with 2 inches of water and nutrient solution.
pic Ed Rosenthal

This article appears in Volume 5 – Issue 4 of SKUNK Magazine.

MANY OF YOU, I’m sure, are already familiar with the concept of hydroponics and the systems involved. For those who aren’t, hydroponics is the method of gardening in which plants are supplied with nutrients through solution in water. Gardeners have a choice of systems to accomplish this: Deep Water Culture (DWC); Drip, Ebb and Flow; Nutrient Flow Technique (NFT); Reservoir; and Wick. All of these are available as commercial units but can also easily be constructed at home.

Hydroponic systems vary in their complexity and the amount of care they require. However, the simplicity of construction or difficulty of maintenance does not necessarily infer that the crop will be larger or of higher quality.

The systems fall into one of two broad categories: passive or active. Passive systems, such as reservoir or wick setups, depend on the molecular action inherent in the wick or medium, sometimes referred to as capillary action, to make water available to the plant. Active systems, which include ebb and flow, nutrient flow technique and deep water culture, use a pump to provide the plants water and nutrients.

 

THE RESERVOIR SYSTEM

The reservoir system is by far the easiest system to set up and maintain. Plants are grown in ordinary plant containers of the chosen size. The containers are placed in a tray surrounded by walls – usually 4”-6” high.

The containers are filled with clay beads. Alternatively the bottom third of the container is filled with beads and the top portion is filled with a hydroponic mix such as vermiculite — perlite, peat moss (Sunshine Mix #4) or even a non-hydro planting mix. The container is placed in the tray, and sits directly in a hydroponic nutrient-water solution with about 20-25 % of the container immersed in the water. A container with soil 4” high should be immersed about an inch deep. A 12” tall container should be sitting in 2 ½-3” of water. This may be the most inexpensive system and the fastest one to set up:

 

 

STEPS TO SETTING UP A RESERVOIR SYSTEM

  1. Obtain enough clay beads to fill the containers.
  2. Rinse the beads in water until the pH tests close to 7, neutral.
  3. Pour the neutralized LECA (Lightweight Expanded Clay Aggregate) into appropriate sized containers.
  4. Place the containers in the tray.
  5. Water the containers from the top to get started. Make sure the planting medium and wicks are thoroughly moistened.
  6. Mix nutrient/water solution.
  7. Test the EC or PPM of the solution.
  8. Add a small submersible pump in the tray to circulate the water.
  9. If the room temperature falls, it may cool the water too much. Add an aquarium heater to the tray.
  10. Use a sheet of white/black polyethylene or other opaque cover to place over the tray. The cover keeps light from getting into the nutrient/water solution, where it would promote algae growth.

 

* Optional Accessories: water reservoir regulated by a float valve. The water level of this system should be maintained at a fairly stable level. As the plants grow they will use larger quantities of water so it will have to be replaced more frequently as the garden proceeds towards flowering.

 

EQUIPMENT

  • LECA (Lightweight Expanded Clay Aggregate)
  • pH test meter or pH test paper
  • Planting containers
  • Tray with walls of appropriate height
  • Hydroponic Nutrient Solution
  • EC or PPM meter
  • Submersible pump
  • Aquarium heater
  • Tray cover
  • (optional) Reservoir
  • (optional) Float valve

 

This is an excellent technique for use outdoors since the container has its own limited reservoir. The only problem is that a container with no holes can get waterlogged. To prevent this, place overflow holes at the maximum water level. If more water pours into the container, it will flow out of the hole, leaving plenty of air for the roots to respire.

This technique can be adapted so that containers have internal reservoirs. The bottom 20% of the container will be filled with water. A gauge can be placed in the container to measure the water level. One method is to use a plastic tube with some holes drilled in to allow water to enter and exit freely. Place it into the container and stick it in surrounding pebbles so it is held vertically. Take a thin wooden or plastic rod and affix a cork on the bottom of the straw using silicon glue. A bamboo stake also works well for this. Place the stake in the tube. The cork will float on top of the water, pushing the rod up to indicate water level. Mark the rod so it shows maximum desirable levels. To drain water from the pot, remove the rod and insert a small tube attached to a pump or siphon.

Another gauge can be made using a piece of transparent flexible plastic tubing. The tubing is inserted into a hole at the bottom of the container and silicon glue is used to prevent leaks. The tube is attached vertically to the side of the container so it indicates its water level. To drain water, change the tube’s position.

Several containers can be connected to a single reservoir regulated by a float valve, which is connected to a reservoir using tubing.

Water should be added to containers with drains sitting in trays from the top down so that any buildup of nutrient salts caused by evaporation gets washed back out of the container into the tray.

 

THE WICK SYSTEM

The wick system is inexpensive to construct and easy to set up and maintain. The planting container is held above a reservoir. Both ends of braided nylon rope hang from holes in the bottom of the container into a reservoir filled with water/nutrient solution.

The principle that drives this system is capillary action, the same physics that draws water up a napkin. As the water is removed from the wick, the water molecules above draw neighboring molecules towards them to maintain the electrical charge and ultimately equalize water tension. As a result, with no work on your part, the wick maintains moisture by drawing up water as needed.

The wick is made from braided nylon rope. The diameter of the rope increases with the size of the container.

 

An ordinary nursery container, a bucket or even a soil bag can be used. Before the container is filled with planting mix, install the wicks in the container. They should be long enough to stretch from the bottom of the reservoir through the bottom or side hole of the container, then exit the hole on the other side and run down to the bottom of the reservoir. Each container should receive two wicks at 90° angles.

When nylon rope is cut it starts to unravel. Bind the ends together using silicon glue or by heating the end with a jet flame.

Keeping the holes in the container small makes it difficult for roots to penetrate to the reservoir. Keeping the roots from growing down the wick into the reservoir may be a matter of convenience. However, once the roots hit the water, both their growth and the growth of the plant spurts because the roots now have access to cheap water and nutrients.

The wick system is self-regulating; the amount of water delivered depends on the amount lost through evaporation or transpiration. More than monitoring the containers to check to see that they are moist, with the wick system the main thing is to keep your eye on the reservoir. As long as the reservoir has water, the plants are being watered.

A number of different mediums can be used as planting mixes for wick systems. Virtually any planting mix can be used since soils generally draw water. Using a planting mix has the advantage of providing the plants with a nutrient-rich base that can be supplemented using water/nutrient solution. If the medium does not seem to be drawing water and is too dry, adding 20% vermiculite to the mix will add drawing capacity.

A mix consisting half each vermiculite and perlite provides a non-nutritive medium that is easy to work with, has a nice consistency and draws water well. Using vermiculite-perlite allows you to have complete control over the nutrients being supplied to the plants. Adding 10% worm castings or compost increases the microbial life and provides a substrate for them to thrive. Their symbiotic relationship with the roots increases plant vigor and growth.

Each medium has a maximum saturation level. Beyond that point, an increase in the number of wicks does not increase the moisture level.

 

 

STEPS TO SETTING UP A WICK SYSTEM

  1. Install the tray in the grow space.
  2. Find a support to raise the containers 4” – 6” from the bottom of the tray. Wood blocks, pallets and cement blocks all work well.
  3. Measure distance from bottom of the tray through the container and back to the tray bottom. Cut the nylon rope. Seal ends.
  4. Place rope in containers. Tape or glue in place.
  5. Fill containers with planting medium.
  6. Place containers on supports, making sure the wicks hang down to the bottom of the tray.
  7. Fill the tray with nutrient-water mix.
  8. Water the containers from the top to get started. Make sure the planting medium and wicks are thoroughly moistened.
  9. Mix nutrient/water solution.
  10. Test the EC or PPM of the solution.
  11. Add a small submersible pump in the tray to circulate the water in the tray.
  12. If the room temperature gets cool, it may cool the water too much. Add an aquarium heater to the tray.
  13. Use a sheet of white/black polyethylene or other opaque cover to place over the tray. The cover keeps light from getting into the nutrient/water solution, where it would promote algae growth.

 

*Optional Accessories: Water reservoir regulated by a float valve. The water level of this system should be maintained at a fairly stable level. As the plants grow they will use larger quantities of water so it will have to be replaced more frequently as the garden proceeds towards flowering.

 

EQUIPMENT

  • One tray
  • Support for containers: pallet, cement blocks
  • Nylon rope of appropriate diameter
  • Planting containers
  • Tape or glue
  • Planting mix
  • pH test meter or pH test paper
  • Hydroponic Nutrient Solution
  • EC or PPM meter
  • Submersible pump
  • Aquarium heater
  • Tray cover
  • (optional) Reservoir
  • (optional) Float valve

 

No matter which of these hydroponic systems you choose, the systems are easy to make and easy to maintain. Once you get the hang of it, you will probably want to experiment and use your ideas and experiences to develop your own system.

 

Be sure to read part 2 of this article by clicking here.

 

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