Aquaponics in a Nutshell

Tilapia enjoying a nice morning swim My new life as an urban farmer is off to an excellent start.  I am making friends and, everywhere I look in Chicago, there are Windy City Harvest graduates doing excellent things to improve the food system.  I am on a good track to make the difference I feel compelled to make.

When I tell people about my program, I usually mention the aquaponics system at WCH, because it is a bit of a buzzword, especially as marijuana becomes gradually more legal around the country.*  You can absolutely use aquaponics to grow pot, but that's not really why it was designed.  We had a lecture on aquaponics today, and it was incredibly illuminating, and I'm not just talking about grow lights (haha!).

The guy who designed and runs the aquaponic system at WCH is a very knowledgeable individual named Andy.  We are not formally trained in aquaponics as part of our certificate program, but he said that the same science behind horticulture follows through to aquaponics and he's totally willing to teach people the basics one-on-one as time allows.  So, I only know what Andy was able to squeeze into a 1.5 hour lecture, but I will do my best to regurgitate the main points below.

First, where does the word "aquaponics" come from?  Well, there was hydroponics, the growing of plants in nutrient solution without soil, and there was aquaculture, the raising of fish in pools for the sake of food.  Both of these systems of food production, while innovative and interesting to think about, are immensely wasteful.  Hydroponics doesn't really have a good solution for what to do with plant waste water, it's very costly to set up, and the systems are very susceptible to mold issues. Aquaculture is a big polluter; you are essentially setting up a cattle feed lot for fish. Aquaponics, however, uses the waste nutrients from the plants to nourish the fish, and the waste from the fish to feed the plants. The crucible for development in aquaponics was the Virgin Islands in the 1970's.  It is really something we can thank the hippies for.

It is a bit more complicated than that, and you do have to feed the fish, but the cycle is way more sustainable than keeping the two separate.  The water that starts in the system stays in the system.  The only waste is a little solid waste from the fish, but there are ways around that as well.  Thus, the number one advantage to an aquaponic system is water conservation.  In addition, you don't need soil, you minimize pollutants going into the ground water, and the systems are incredibly adaptable and scale-able. Andy gave us an example of a home sized system, with a 10 gallon tank for a couple fish and a plastic tub on top for the plants.  You could have fresh basil, mint, bok choy, and some types of lettuce year round with this type of set up.  The initial set-up cost would be around $50 and that would pay for itself in a winter or two.

Individual home-sized aquaponic set-up

There are challenges to this type of system, as there are with anything.  It takes a bit of an engineering mind to build out a system to begin with, and evidently sometimes you don't know if you are doing something wrong until basically the whole system fails.  I mean, pretty much any science/trade/field has critical points of failure, but in this case, you could lose a lot of time and money if the system you put together has a critical flaw.

Once your system is set up, you become the grandmaster of tedious balance of pH and nutrients.  Andy showed us a really lovely chart that lists the 10 most essential nutrients for plants and the pH at which they are most available to the plants in solution.  It is in the slightly left of neutral range of 6.5 to 7 pH.  Any more acidic and things start to die.  I didn't take great notes on the actual processes and chemical conversions that are going on, but the basic cycle is as follows: feed fish, fish exhale ammonia through gills, ammonia is consumed by nitrosomous bacteria which turn it into nitrites, which nitrobacter bacteria eat and turn into nitrates which are the lovely nitrogen rich compounds that make plants super happy. Most systems do produce some waste at this point, which can be composted. However, at WCH they have an intermediary bed system, which has different plants in coconut coir for aeration, sitting in puffed shale that has red composting worms living in it. The worms feast on the extra bacteria and waste from the fish, so the system itself has basically no solid waste.  The other boon to this approach is these shale composing beds can support more intense root systems. So you can grow tomatoes, hot peppers, peas, and so on, making the whole system more profitable and/or delicious, depending on your perspective.

So, basically, that's aquaponics in a nutshell.  If you have a flair for tinkering with pipes and fish and plants, it might be a good hobby for you.  Some folks who do aquaponics grow enough fish to sell them to processing companies, but it's mostly tilapia, and the vast majority of tilapia are being grown way more cheaply in other countries in polluted waters. Andy says that WCH is planning on moving from tilapia to koi, mostly because they don't grow enough fish to keep a regular distributor.  Koi can be sold for way more money as ornamental fish once they outgrow our aquaponics system.

See more pictures below and let me know if you have other questions about aquaponics.  I'm soon to learn all about soil science, so I will have a better idea of what specific types of plants need in their soil at an elemental level.  Exciting stuff!

Basil growing in the floating beds

Cucumbers growing in the media beds, fed by the worms

Sump and pump directly below the media beds

* I honestly know nothing about marijuana, having never touched the stuff, but you do you, friends!