Notes from Windward: #66


Our Approach to Studying Aquaponics

it's a matter of scale

     Windward is focused on exploring ways to create a critical mass of sustainability, a quest which involves studying new approaches to the challenge of feeding, fueling and clothing people using sustainable practices at the small community level. Part of our premise is that we want to work on systems which contain the potential to create fundamental change for the better rather than spend time on things which can at best can only make inherently flawed systems less bad.

     We believe that hyper-integrated aquaponics has a key role to play in creating sustainability for local communities, but anytime you undertake to work with a dynamic, nature based system it's easy to become overwhelmed by the many ways that such systems can crash -- which is one reason why folks in the field of aquaponics half-jokingly refer to themselves as "serial fish killers."

Virgil gives scale to the micro-aquaponics setup


     Since research is what you do when you don't know what you're doing, and since we want to kill as few fish as possible as we work our way up the learning curve, we proceed from the principle that it's best to start with the smallest, simplest system possible and work your way up from there.

      Consequently, we actually have three aquaponics systems under development. The first is a micro-system with sixteen square feet of grow beds and about 40 gallons of fish tank capacity. The primary objectives here are (1) to get the hydraulic parts of the system working correctly as we hone our ability to (2) control system pH and (3) develop "seed cultures" of the two types of bacteria needed to make this work.

     When thinking about aquaponics, it's easy to focus on the fish and the plants you want to grow, while overlooking the fact that it's the bacterial culture resident in the pea gravel that makes the system work. Forgetting that is a good way to kill fish.

      Assuming that the water flow is working correctly, it takes about two weeks for the first type of bacteria to get established and generate notable amounts of ammonium nitrite. Once that happens, it takes another couple of weeks for the second type of bacteria to respond to the availability of nitrites in the water and populate the pea gravel to the point where the nitrites are being readily converted into the nitrates which the plants can use. Once both type of bacteria are well established in the micro unit, we can use those populations to stock other, larger grow beds with the necessary strains.

     Once the nitrate levels start to rise, you can begin the gradual process of adding plants and cheap goldfish in an even manner that balances out the needs of each part of the system. And while it's more challenging to keep a small system in balance, a small system offers the advantage that it's much easier to dump and start over when you need to hit the "reset" button.

adding pea gravel to one of the
mini-aquaponic grow tanks


     While we're working with the micro-aquaponics system, we'll be continuing construction on the mini-aquaponics system. This system will feature almost one hundred square feet of grow beds and a 1,250 gallon fish tank. The tank will be buried in the ground and will allow us to over winter fish such as carp or trout.

     Once we've learned as much as we can from these two smaller system, we'll be ready to construct the full-scale system in a special-built solar greenhouse with above-ground, insulated tanks and about 360 square feet of grow beds capable of producing plants and fish year-round by using "waste heat" from our pyrolytic/solar electrical plant.

an illustration from the building permit for our 20'x60' solar greenhouse


     Hope that helps clarify what we're referring to when we talk about the micro and mini aquaponics setups we'll be working with.

Notes From Windward - Index - Vol. 66