Aquaponics experiment 2013

Posted on January 6, 2015 in DIY, Portfolio

During the summer of 2013 I designed and constructed my first ever aquaponics system and wrote a series of articles week-by-week to show the ups, the downs and all the lessons I learned while maintaining it. Being a budget-conscious graduate student at the time I made sure to keep the costs down wherever possible, resulting in an overall investment of about $200. Now that the project is completely finished, I can round up all the important information and pass it along in one nice post!

What is aquaponics?

Aquaponics is a combination of aquaculture (raising fish) and hydroponics (growing plants without soil) in a symbiotic system [1]. The fish generate waste, which is converted by bacteria growing throughout the system into beneficial nutrients that help the plants grow. The remaining water is then returned to the fish tank, creating what is known as a nitrogen cycle. When an aquaponics system is set up properly it will take care of itself pretty well and only require the owner to feed the fish on a regular basis!

Design

I began researching aquaponics systems several months before designing and constructing my own, learning all about the science that goes into them and the various types of designs, fabrication techniques and shortcuts shared by many generous enthusiasts all over the web. Most importantly I learned that once you understand the fundamentals of what makes these systems work you can change quite a few things and still have a functioning system! Perhaps this is why it seems like everyone’s system looks different.

In general, every aquaponics system by definition pretty much must contain the following:

  1. Fish tank (FT): a water-tight, fish-safe enclosure to keep the fish in. I used a 110 gallon stock tank from a local agriculture supply store.
  2. Grow bed(s) (GB) with growing media: a bed of material that will provide structural support for the plants while allowing for lots of water and air to reach the roots. Should be about half the volume of the fish tank. I cut a plastic 55 gallon drum in half for the beds, and filled them with pea gravel.
  3. Some way to get water to and from the grow beds and fish tank: some combination of pumps and siphons, with various plumbing bits like bulkheads and tubing, to transport water throughout the system. I used a 185 gph submersible pump in the fish tank and loop siphons on the grow beds.
  4. Fish: something hardy and tolerant of potentially harsh conditions. Common species like catfish, tilapia and goldfish are best. I went with channel catfish.
  5. Plants: just about anything you would conventionally plant in the ground. Some species may take to aquaponics better than others, but very few will not take to the process at all. I stocked my grow beds with cherry tomatoes, lettuce, broccoli, cucumbers, jalapenos, eggplants and squash.

Using all the information I had gathered, I was eventually able to fire up Sketchup and create a decent plan for how I wanted to construct my system:

Sorry in advance if I’ve left anything out of the list, there was a lot of hacking with scrap materials in this project!

Construction

support-with-beds-and-gravelBuilding out the system was fairly straightforward and was quite manageable with basic power tools and a box of screws. The wooden support structure was constructed entirely of 2x4x8 studs, onto which two grow beds fastened out of two halves of a 55 gallon drum were placed.

A 110 gallon stock tank was set on a pallet to provide a bit of an air gap in the hopes of preventing excess heat from the concrete floor radiating into the tank. A powerful submersible pump was dropped into the tank, then connected to a simple plumbing system made of black vinyl tubing and a barbed tee in order to transport and distribute water from the fish tank to the two grow beds.

A couple of bulkhead fittings on the grow beds allowed me to connect large clear vinyl tubes near the bottom of each bed for drainage. At first I directed these tubes into buckets so I could (very) thoroughly wash the cheap pea gravel I dumped into each grow bed in order to prevent excess dirt from building up throughout the system.

Once the pea gravel was nice and clean I turned these vinyl tubes into loop siphons, which automatically drain all of the water in each grow bed once the water level has reached a certain height. I can’t tell you how exciting it is to see this ancient technology work for the first time with no power whatsoever!

More photos of the construction process can be found in the following albums:

Cycling

Cycle Image1One of the most important aspects to building a successful aquaponics system is establishing all the necessary bacteria that converts fish waste into a form that the plants can make use of. Establishing this bacteria creates a ecological “cycle” through which nitrogen is converted into various forms. You can learn much more about the nitrogen cycle elsewhere, but here is a birds-eye overview of what it does:

  1. Fish produce waste, which contains high levels of ammonia, which can become toxic to the fish if it builds up too much. Also, the plants can’t do much with it.
  2. Bacteria consumes the ammonia in the fish waste and converts it into nitrites, also toxic to the fish.
  3. Other bacteria then consumes the nitrites and converts them into nitrates, which the plants absolutely love. This is what serves as a food supply for the plants.

The experts say that you should spend 3 to 6 weeks waiting for the bacteria to become established before adding any fish or plants. However, there are a few shortcuts you can take to bring this down quite a bit, each with their own tradeoffs. I chose to add fish to the system on day 1 (because obtaining fish was pretty difficult and I couldn’t really choose when I got them), which helped jump-start the system by providing ammonia to attract bacteria. I also used a bottle of Nutrafin Cycle, which is basically a bottle of concentrated live bacteria that you can dump directly into your system to get things rolling right away.

All in all it took about five weeks for the system to become fully cycled with fish and plants installed!

Adding fish

channel-catsOriginally I planned to add just 5-10 fish to the system, and in fact that is all I signed up for through my fish dealer. However, when the dealer got to town it became obvious that the minimum order was about 25. Not because of economic reasons, but because that is how many fish would come out of the tanker truck when they opened and closed their valve as fast as they could!

So, I went home with around 25 fish, about half of which I planned to sequester in buckets to the side for a few days in the hopes of giving my system a fighting chance of ramping up the beneficial bacteria to accommodate all the newcomers. Unfortunately, these fish didn’t survive the night in their buckets and therefore never made it into the system.

All of the other fish (at least 15) made it through the initial introduction to the system and helped stabilize the system by providing a continuous source of wonderful, fresh, nitrogen-filled fertilizer.

Adding plants

As soon as the fish were added I went out and bought a bunch of plant starters and popped them into the grow beds. I spaced them all a few inches apart to make sure they had plenty of room for their roots to reach out through the pea gravel all around them.

  • On the left: six lettuce plants and six broccoli plants
  • On the right: five cucumber plants, one squash plant, a cherry tomato variety, a jalapeno variety and some eggplant

Maintenance

Chemical testing results of cycled systemOnce the system has been set up and the nitrogen cycle has had enough to time to establish itself there is actually very little to do in the way of maintenance and upkeep! In fact, I can only think of four things that I really had to do all summer to keep things going:

  1. Feed the fish: catfish will eat as much as you feed them, but more food means more waste. I fed them about once a week and barely used any of my 20lb bag of fish food!
  2. Tweak the siphons: sometimes my loop siphons would pinch themselves closed, or shift slightly as the hot summer sun softened them, or (near the end) filled up entirely with algae blooms. All very easy problems to solve!
  3. Run chemical tests to make sure the system isn’t in danger: using a freshwater testing kit I was able to test the water’s pH, ammonia, nitrate and nitrite levels in about 10 minutes to see how everything is doing week by week.
  4. Very occasionally clean the pump or other plumbing bits: sometimes too much waste or junk will build up on the pump’s filter or (rarely) inside the black vinyl tubes of the plumbing system. A quick rinse in water, and sometimes some compressed air, did the trick!

Plant growth

Visiting the system every day and seeing how much everything had grown from the day before was a constant source of joy for me throughout the summer. I was absolutely astounded by how big and how fast all of the plants grew! I had tried doing some patio gardening in pots before and had never achieved growth like this! Nearly all of the plants grew to an absolutely massive size and produced lots of delicious food, which I eventually had to resort to just giving away to anyone who wanted.

However, two of the plants did not fare so well; specifically the cucumbers and squash. The cucumbers were never able to get past the flowering stage, whereas the squash produced a solitary, baseball-sized melon on a sickly-looking vine. It’s hard (for me, at least) to say why these two particular plants didn’t do so well, so if you have any thoughts please feel free to let me know!

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Initial planting - left
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Harvesting

Once all of the plants had grown out for a bit (about a month or so) they were ready to harvest. Better yet, most of these plants continued producing harvestable foods until the start of fall!

  • Tomatoes: highest yield plant of the lot. About a handful to a dozen tomatoes were harvested a few times a week. Tasted just like what you’d buy at the store, if not a little better, especially on warm days!
  • Broccoli: six plants produced about two good heads each before the season was up. The heads were just as good as any I’d bought in a store.
  • Jalapenos: not as abundant as the tomatoes, but did produce a couple dozen jalapenos. Tasted just like any store-bought jalapenos.
  • Eggplant: did produce a handful of eggplants, but they were all very small and not particularly tasty.
  • Lettuce: harvestable almost immediately, and quickly began producing more leaves than I cared to use. Eventually I learned that if you don’t pick the leaves at the right time they turn sour.
  • Squash: a single, baseball-sized melon that appeared OK, but tasted somewhat bland.

Winter

heaterOnce all of the plants stopped yielding in the fall, I tore out all of the plants and removed the loop siphons so that water from the fish tank is pumped into the grow beds and continuously drained back to the fish tank. My thinking was that this would keep the water moving (making it harder to freeze in the winter), allowing it to continue being filtered by the bacteria inside the plumbing system and the grow beds. This also would help to keep introduce oxygen into the fish tank, which I hear is important.

To help keep the water from freezing, and to give the fish a little more comfort for the winter, I dropped in a 300W adjustable heater.

I continued to feed the fish, but only about once a month. Even still, this was enough to make the water pretty foul near the end of the season. Nonetheless all of the fish who were alive in the fall survived the winter! Amazing little creatures!

Teardown

Eventually winter passed and the temperatures rose to a more comfortable level, so it was time to tear down the system. Since I was moving to Omaha at the beginning of the summer, and the location I installed this system at was not going to be available anyway, I disassembled everything and stored it away. I kept the grow beds, fish tank, plumbing bits and electrical gizmos, so hopefully I can revive this project again someday!

As for the fish, I rounded them all up and released them into a local lake so they could live out the rest of their natural lives in relative peace.

Conclusion

Overall I think this project was a huge success! After much caution and sometimes disheartening feedback from various online communities early on, I quickly learned a very valuable lesson: it’s more difficult to fail at aquaponics than it seems! Whenever I posed a question online, or searched forums for advice on a problem I was having, it seemed like the standard response was, “buy this expensive thing and read these five books, otherwise all of your plants and fish will die in the first week.”

As you can see, nature is much more forgiving and resilient than that. While I certainly did not have a perfect system, the results I had far exceeded my expectations and gave me many months of great learning experiences. And for a total investment of about $200-$300, what can I possibly complain about?

Now I know more about how to make a more successful system next time so that I can not only harvest a bunch of veggies, but raise some catfish suitable for cooking as well! Can’t wait until I can build another system!