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Basic hydroponic rockwool system

Introduction

The basic system we are discussing is based on commercial use for growing marijuana plants. The intent is only for a mono-cultural style of cultivation, and would not work with a mixed garden. The design recirculates the nutrient solution, so if you plan on using a total-loss system, you must find a bigger tank and make adjustments for run-off. There will be differences between the recirculation method and the total-loss method.

We highly recommend this system for larger marijuana gardens as a basic hydroponic system that uses rockwool in combination with these provisions:

  • You will need upper level support for the vines of your marijuana plants for this system.
  • This system is designed for using aqua trays placed within steel channels. The trays are 4.3' (130 cm) long and each contains a single slab. Each crop will determine plant spacing, but typical range is 2-6 plants on each slab.
  • Steel channeling is what we recommend most for holding the aqua trays. You can use whatever you find at your local sheet metal workshop. You will need the lightest gauge they carry and you will need it galvanized. You will also need plastic sheeting to protect the nutrient solution from the metal. You will also need a bit more to collect the run-off from the end of your channels to return your nutrient solution to the tank.

Layout

  • The way your system is set up will tell you where your tank needs to go. It has to be lower than the ends of your channeling and placed near the end of a hose or a spigot.
  • You will want at least 2L of nutrient solution for each marijuana plant within your system. If you have room for more volume, that is preferable.
  • You want each dripper to flow at the same rate whenever possible. A stopwatch and a jug should help you get this timing down. Big systems may not have equal pressure among all plants, leaving some under-nourished, so you will need PVC piping to connect your joints to equalize the pressure within your system. Each dripper needs to be able to get the right amount of solution to each plant when you feed. If you need an extra pipe, just make sure you cap off the end to avoid spilling.
  • Between your pump and drippers, you will need a pump to remove impurities and avoid any blockages. Check it often to keep it clean.
  • Don't forget to include a bypass between your tank and your pump. It is required to help control the supply that goes to your drippers and to ensure your pump is running freely and adding in the most oxygen possible to your nutrient solution. Adjust the gate valve located on your bypass to control your water supply as necessary.

We know this system is incredibly simple, but you do need to keep a few things in mind. You want the largest tank you can practically have in your location. This is to lessen the effects of any pH or conductivity changes within your nutrient solution. This will also allow you to get a lot of oxygen within your solution, helping your plants grow even better. The extra pumping that a large tank can offer will help with all of these issues.

Summary of common hydroponic systems

Pot culture

Advantages

  • Inexpensive set up
  • Simple design
  • Adaptable for nearly any plant you would want to grow
  • Plants remain mobile to help optimize plant spacing
  • Plants are not vulnerable to power outages or failures of pumps

Disadvantages

  • Often requires you to water by hand
  • Requires a lot of washing of pots and Perlite
  • Labor intensive

NFT (Nutrient Film Technique)

Advantages

  • Wonderful performance
  • Can usually be completely automated
  • High yields from plants
  • Little or no waste

Disadvantages

  • Setup costs more than Pot Culture does
  • System works the best with just one crop within each system
  • Plants are quite vulnerable to a pump failure or a power outage
  • Requires users to have some basic mechanical knowledge

Rockwool (Slab culture)

Advantages

  • Excellent performance
  • Can typically be automated
  • Less vulnerable to a power outage than an NFT system

Disadvantages

  • Setup of the system can be difficult
  • Plant mobility is greatly reduced

This overview was intentionally brief so that you could get the basic ideas of how hydroponic systems work. You will need to decide which to use based on which crop you intend to grow and how much money you can invest into the system. We recommend you read up more on each system before making a decision or spending money. The many books on each topic are a good idea to consult.

Want to read more about marijuana? Go to our marijuana grow guide.

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