The pilot scale

We’re doing a pilot scale aquaponics system this summer. Folks have been doing aquaponics all over the world for years now. In fact, the research program at University of the Virgin Islands run by James Rakocy that arguably launched aquaponics is right here near us, so there’s already a lot of aquaponic know-how for the humid tropics and subtropics.

A super-fancy diagram of the pilot system. L to R, we have the fish tank, the radial-flow clarifier, and the plant bed. The spigot to flush out solids at the bottom of the clarifier and the second bed running back towards the fish tank aren't shown in this very condensed profile view.

A super-fancy diagram showing the basic gist of the pilot system. L to R, we have the fish tank, the radial-flow clarifier, and the plant bed. Not shown due to space: the spigot at the bottom of the clarifier for flushing out the settled-out junk, and a second veggie bed running back towards the fish tank.

However, there are a few things that we want to do that would be new for aquaponics in this region (as far as we know). We want to see if we can grow lettuce year-round on a commercial scale. As far as I can tell from scouring the literature, lettuce does ok in warm temperatures as long as you harvest it before it bolts– and since it grows fast in aquaponics, that shouldn’t be a problem. However, when the water temperature gets above 80F you start to get outbreaks of “tropical Pythium.” It’s a fungus that eats on the roots and turns them into slime.

The UVI system raises lettuce only in the winters because tropical Pythium wipes their lettuce out every summer. We’re going to try and see if we can keep it at bay. There are lots of management techniques that can be done to mitigate it even without using fungicides; the most relevant for us will be keeping water temperature below 80F, because we also want to try some fish species that become stressed above 80F. Tilapia are great, but their markets are becoming saturated by large producers and there are much better fish out there, gastronomically and nutritionally speaking. We’ll use tilapia for the trial period because they’re hardy and if we have hiccups we won’t have to throw out dead fish and start over. Once we have good control over the system, though, we’ll branch out into some others.

How to keep water below 80F in the summer in Florida? Stay tuned….

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