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Scaling Up to a Larger Aquaponics System – Part 2

Previously in Part 1 of Scaling Up to a Larger Aquaponics System, I talked about how the aquaponics system was put together. Here in part 2 of this 4 part series, I will cover system startup and operation.

Starting Up the System
To get the system running, I needed fish. I was determined to try tilapia, which are probably the most common fish in aquaponics systems. I ordered the fish from a supplier in Florida. If the weather were warmer, I could have added the fish directly to the fish tank. But it was still quite cold in Georgia. Tilapia take about 7-8 months to grow large enough to harvest. By October it would be too cold here for them to survive. This meant that I would need to get fish that were born in February when it is still too cold for them.

To accommodate this timeline, I needed to raise the fish in an aquarium for 4-6 weeks until the water was warm enough outside. Because I ordered 100 tilapia fingerlings, I set up two 20 gallon aquaria with supplies from the local pet store. I got them operating a few days before the fish arrived so they had time to reach equilibrium.

The fish were shipped in double plastic bags inside a Styrofoam insulated box. I was wondering how fish would be shipped but they all arrived safe and alive. As soon as I got them, I transferred 50 into each aquarium. The 20 gallon aquarium didn’t seem too crowded when the fish were very small. I quickly learned that the aquarium got more crowded as they grew. I wanted them to grow fast so I fed them as much as they would eat for the first few weeks. One consequence of the crowded aquarium was a rapid build-up of ammonia. I found myself having to do partial water changes every day to keep the ammonia level down. If I were to do this again, I would come up with a better plan for this part.

Tilapia in 20 Gallon Aquarium

Tilapia in 20 Gallon Aquarium

I rolled up my sleeves and did the daily water changes to keep the fish healthy. The ammonia “waste” water was not wasted. It was added to the fish tank outside to get the biological filtration going. I filled the fish tank with water from my rainwater catchment tanks and started the circulation. The ammonia from the aquarium water changes fed the bacteria to begin the conversion to nitrites and nitrates. While I was waiting for the temperature in the fish tank to be warm enough for the tilapia, I purchased some feeder goldfish from the pet store and added to the tank. These helped to get the biological cycle going sooner.

Adding Tilapia to the System
Once the water temperature in the fish tank reached about 70 degrees, I was comfortable that is was time to move the fish. I should mention that the plan all along was to put half the fish in the aquaponics system and half in our cement pond. To prepare, I slowly lowered the temperature in the aquaria over a few days to match the water temperature of the big fish tank. On moving day, I moved a few fish at a time to the tank. They seemed to get accustomed to the larger space quickly and disappeared to the bottom.

For the next week or so, I fed the fish as much as they would eat 3 times a day. The goal was to build up the ammonia to fuel the bacteria. Unlike the aquarium, it wasn’t a concern that the ammonia levels would become toxic in a system with over 300 gallons of water. In fact, I wanted as much ammonia as I could get. The six grow beds contain a lot of grow media for the bacteria to colonize, so the system can handle a lot of ammonia.

As I’ve described before, the biological filtration cycle involves two types of bacteria. The first type converts ammonia to nitrites and the second type converts nitrites to nitrates which are plant food. It can take as long as 30 days for a new system to reach a balance with enough nitrates to support vigorous plant growth. So it is important to get the system up and running as quickly as possible so you can start adding plants. That’s why I added goldfish earlier and fed the fish as much as they would eat. To monitor the levels in the water, I used my test kits for ammonia, nitrites, and nitrates. Testing takes the guess work out of it. Once I saw the nitrate level starting to increase, it was time to add plants.

Adding Plants to the System
Since this was still a bit of an experiment, I wanted a variety of plants to see which ones did better. I planted yellow squash, cucumbers, kale, spinach, peppers, and sesame. The sesame was a donation from my neighbor. I wasn’t familiar with the plant but I thought it was worth a try.

A Freshly Planted Cucumber

A Freshly Planted Cucumber

The plants are prepared by carefully removing all dirt from the roots and rinsing them off in water. We do this to avoid an unnecessary build-up of soil in the system. After a location is chosen in one of the grow beds, the grow media (rocks in my case) is moved aside to form a hole. The plant is placed in the hole and the rocks are gently placed around the roots and stem to hold it in place. Now you let the system do its thing and wait.

What’s Next
Next time in part 3 of this 4 part series, I’ll cover the results with lots of pictures. This is the cool part when you see how amazing the growth of the plants is, so please join me.

Resources for this post:
Introduction to Aquaponics
My First System: A Small Scale Aquaponics System
Building the larger system: Part 1 of Scaling Up to a Larger Aquaponics System

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