Learning Opportunities

Large tanks for aquaponics are expensive.  Constructing tanks for fish is a lot of work and the lining is pricey.  Plastic tanks over a hundred gallons or so get expensive fast.  I started collecting large stock tanks off Craigslist, and even managed to buy a few of the IBC containers that are so popular on the Aquaponics websites.

Ultimately I want to build a large system and capitalize on the stability of larger bodies of water and the economies of scale.  I would like to combine this with my other greenhouse work, reaching out the community and providing unusual opportunities and crops.  But first I needed to know what I’m doing.

2'x3' media beds filled with 3/4" expanded shale. Lettuce direct seeded into the near bed.
2’x3′ media beds filled with 3/4″ expanded shale. Lettuce direct seeded into the near bed.

Distractions and false starts aside, I finally built a small closed system in my indoor office in 2013 so that I could study the dynamics of the system.  I incorporated NFT (nutrient film technique, utilizing water running down narrow channels to feed small net pots of plants) and two flood and drain grow beds.  These lived on two shelves of a large wire shelving unit, with grow lights above them and the 40 gallon fish tank on the bottom.  A couple dozen small koi were stocked and I’ve tried growing various things in the system with mixed success.  Which is great, because I learned a lot from every failure.

koi in a small aquarium
Aquaponic filtration allowed me to raise an unbelievable number of koi in a small aquarium.

This system was still running while I setup my new system last year.  The fish were up to 12″ long, and they went into a greenhouse sump for the winter.  They will grace an outdoor display pond in the coming months.  Meanwhile, I’ve been operating test aquaponics system two, a slightly larger 700 gallon setup in the dome greenhouse.


Elephant ear and other aquatic plants
Elephant ear and other aquatic plants

I’ve been interested in growing plants in water for nearly as long as I’ve been interested in growing plants–that is, most of my life.  Fifteen years ago I was experimenting with various aquatic plant set ups and started raising more and more fish to eat the mosquitoes and provide a healthier aquatic ecosystem.  It just seemed natural to extend the plumbing to the wicking mat benches and into some of the experimental hydroponic setups I had played with.  This allowed the terrestrial plants to benefit from the nutrient rich water, and provided more filtration and stability to the system overall.

Ten years ago, while I was laying the foundations of what would become Mid Columbia Gardens, I stumbled upon the closed loop systems for raising fish and plants that people were beginning to share on the internet.  The name they were giving it was aquaponics, from aquaculture, the raising of fish and aquatic animals, and hydroponics, the raising of plants in water.  I had reservations at the time about the ability of the fish and their food to provide the entire profile of nutrients that the plants required, as well as the ability of the plants to completely eliminate all excess wastes that might build up in the water.

In practice, it turns out that most people are able to supplement and rebalance the water to keep both the plants and fish happy without too much trouble.  It is also common for large systems to export some of the solid waste and turn over small percentages of their water while still retaining primarily “closed loop” recirculating systems.

Temporary greenhouse heating return tank, with fish and young plants
Temporary greenhouse heating return tank, with fish and young plants

These concerns, and sheer lack of time and funds, kept me from looking too deeply into it until someone showed me pictures of Growing Power and their large scale, successful aquaponics operation.  Among other initiatives, they run a large scale fish and plant production greenhouse with unskilled volunteers and a home grown infrastructure.  I can’t do them justice; go check them out at the link above.  Seriously, I’ll wait.

By this time I had cycled hundreds of self-sustaining aquatic systems of all sizes, from 5 gallons to thousands, in saltwater, fresh water, and brackish water.  I was keeping seahorses and koi, snails and shrimp, frogs and crabs.  I also had a good-size non-production greenhouse that had held water systems before the glazing was even on.  I was running radiant heating from the greenhouse ponds through both the air and the soil and using that water as the sole source of watering for all of the plants in there.  The time seemed right to step up to a full aquaponic system.