This week I promised you we would talk about aquaponics.  So today, let's discuss types of aquaponic systems:

The first type of system, the Nutrient Film system, is adopted from the hydroponics community.  In large commercial systems, water and nutrients are constantly pumped through PVC tubes.  Plants rest in holes drilled along the top of the PVC tubes.  This system requires a separate filtration tank to remove fish solids from the water before the water reaches the growing plant roots.   If the solids are not removed,  they begin to build up on plant roots, blocking nutrient absorption.  Separation and treatment of these solids requires space, time and energy.

Another system called the deep water raft system is also very similar to standard hydroponics grow systems.  In this system, however, plants are set in netted pots (like the ones you buy for your garden ponds) on a foam raft which floats over a water tank.  This system can be built at home over an existing aquarium, provided the fish are more carnivorous than herbivorous.  Goldfish love plants, so I’m thinking tiger barbs, catfish, cyclids and maybe some of the tetras and gouramis would be nice for this project.  Maybe you could just add your extra minnows from your latest crappie fishing jaunt.  You should also add an extra air pump and air stone to provide the plants with more oxygen.  This is the system I will attempt to build in my 3 gallon aquarium.  I plan to use it to start seedlings for my larger aquaponic system. 

My larger system will be a basic flood and drain system, specifically the Chop II system by Murray Hallam of Practical Aquaponics in Australia.  This is the third type of aquaponic system.  If you’ve grow sprouts, you’ve done a flood and drain system in its simplest form.  In this system, Unlike the previous two systems, plant beds are filled with growing media instead of water only.  The growing media acts as a biological filter, which is basically a place for bacteria to grow.  This bacteria is going to break down the fish waste (ammonia) into nitrites. Then another, slower growing bacteria converts the nitrites down into nitrates…and guess what? Nitrate is a form of nitrogen plants can use.  Because this process takes place in the grow beds, no extra filtration is needed.  ¾” gravel or hollow clay beads called hydroton fill the grow beds.  Other materials can be used but they may alter the chemistry of the water and cause pH problems later on. Flood and drain systems can grow a wider variety of plants because the roots are exposed to more oxygen.  Water flows into the grow beds, reaches a set level, then flows back out again.  There are many different version of how to get the water from tank to tank and back again and many more will be developed as this potentially world altering food technology evolves.

Here’s where my systems sit:

This week I ordered two more 50 gallon stock tanks and bought another 300 liters of hydroton. I also ordered all my garden seeds for the season and started bok choy, onions, spinach and lettuce seed in my biodome.  Spinach and bok choy are already sprouting inside, daffodils and forsythia are starting to bloom outside.  What’s happening in your gardening world?