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….

Clearing up

Our first task in getting ready to grow fish is to get the trees out of the way. If you’ve ever been to northern Florida, you’ll have seen a lot of these:

A pine plantation

Pine plantations!

Typically a landowner grows them out, and then contracts with a logging company to harvest them. Pulpwood plantations are a big deal in the Deep South, and Owl Springs Farm is no exception. We’ve got about ten acres of sort of little teenage pine trees.

However, it turns out, ten acres is not quite enough for a commercial logging to bother with. Since we now have a different project in mind for that area of land, and
there’s also not a huge amount of ecological value to a monoculture of pine trees, our main priority is just to get them out of the ground before they get too big to take down by Werner’s fancy time-saving logging method.

Our soil here is mostly just sand– so if you ram a smallish pine tree at full speed with a tractor, the whole thing pops out. Roots and all. It saves a lot of trouble coming back to pull stumps out later! I was in the tractor cab with Werner once while he was doing this. You don’t even feel a bump when the tractor hits the tree. Pretty sobering. These are some seriously powerful machines, so safety is key. (For example, no longer riding passenger in a tractor meant to seat one has been a good start for us….)

After that, it’s time to stack the logs somewhere out of the way. We use a different tractor with a forklift attachment for the big logs, but for the smaller ones it’s often quicker just to pick them up.

Werner & Sarah moving a log on foot

Werner & Sarah moving a log on foot


Very short people helping with leftovers!

Very short people helping with leftovers!

Wildlife at Owl Springs Farm

One side of the farm borders a state park, and the other sides are timber plantations and farms, so there’s quite a lot of wildlife in the area. Being northern Florida, it’s a funny run-together of traditional North American and tropical fauna. The farm itself only sees upland species since we’re about a mile away from any open water– an unusual situation in Florida. This includes the usual snakes, raccoons, bats, ibis, bobwhites, sandhill cranes, and armadillos that you’d see in the suburbs anyway all the way up to coyotes, wild hogs, black bears, and panthers. Our one to three freezes per winter seem to be keeping the Burmese pythons at bay so far….

If you look at an official range map for Florida panthers it only shows them living in the deep southwest around the Everglades. The mama and teenage cub Werner saw at Owl Springs a couple years ago can’t read range maps and don’t know that they’re not supposed to be living just an hour away from the Georgia border.

All of you look like dinner.

I’m in ur hayfield stalking ur groundhogs (image source)

If you go into the state park down to the river you’ll find gators, manatees, wood ducks, Naked Ed, and otters. As cool as it would be to have wood ducks and manatees out the kitchen window, it’s important for us as a fish farm to be far away from natural water bodies. The first reason is to keep our domestic fish from getting out into the wild and messing with the ecosystem and/or genetic structure of wild populations.

The second is more for our benefit– it gives us a little buffer zone from critters that eat fish. Panthers and bears might get into fish a little bit, and I’ve never heard of a coyote or a hog going fishing. But gators, herons, otters, and snapping turtles will suck fish down for sure. Otters are particularly deadly in that they’re so fun to watch, I don’t know if I would be very good at chasing them away.

By the way, the name Owl Springs comes from the springs in our area and from a GIANT OWL that lives on the farm. We have a lot of large owls– grey and great horned– even in the middle of Gainesville where I’ve been living for the last several years. This one in particular seems to enjoy keeping an eye on people and is a bit of a fixture around the farm.

Florida’s springs, part II: conservation & innovation

One thing we’re looking to do is adapt some ultra-low-water-use techniques to Florida’s conditions. One of those techniques is aquaponics, or using the wastewater from fish farming to grow vegetables.

Most of the pollution associated with fish farming comes from the first-generation model of aquaculture. Take in lots of clean water. Let the fish poop in it until it’s no longer fit to live in. Throw it out and repeat. It gave fish farming a bad reputation which, frankly, this style of aquaculture deserves. It’s a waste of costly nutrients– fish feed isn’t cheap– that feed algae blooms and other problems that foul up perfectly good lakes, rivers, and coastlines.

Another approach is to run that yummy stuff through some hydroponic vegetables and ta-daa, instead of pollution you have vegetables. Or to put it in business terms: instead of pollution you have more income and jobs for the local economy. Seems like a no-brainer.

Hydroponics is good for cutting down water use too. When you water plants out in the field, especially here where our soil is so sandy it’s like a sieve, a lot of the water you put on plants will run straight down. Water conservation techniques like drip irrigation will reduce this wastage but not eliminate it. When flood, sprinkler, and other traditional irritation techniques are used on our soils, plants will never even see the majority of the water you give them.

On the other hand, hydroponics is a closed system. The only way water leaves in hydroponics is evaporation and transpiration through the leaves. An aquaponic system also loses a bit (1-3% per day) from during flush cycles to remove accumulated waste solids. One of our goals for the pilot scale this summer is to find some constructive uses for the “chunky” flush water. More on this and other water conservation practices later.

Florida’s springs, part I

Our farm is in Florida.

Not this part of Florida:

West Palm Beach. (Credit to

West Palm Beach. (Credit to the Sun-Sentinel.)

This part of Florida.

A spring in central Florida. (Credit to

A spring in central Florida. (Credit to Florida Nature.)

One of the pluses of living on a giant coral sandbar: Florida’s karst geology leads to some one-of-a-kind wetlands (*cough* Everglades), caves, and spring systems.

One of the minuses of living on a giant coral sandbar: it’s rather like being on a raft on top of a swimming pool full of your drinking water, and we all keep peeing in it. Another flipside is that groundwater is so plentiful that it’s taken for granted, and the aquifers are used so heavily that some springs and lakes have completely dried up. It’s especially detrimental in coastal areas that depend on the pressure of fresh water in the aquifers to “push” the seawater out of the way– with that going down, drinking water wells in some parts of coastal Florida have become salty and unusable.

As farmers, this presents a serious dilemma for us. You can’t have local food without local water. At the same time, we have to recognize and reckon with the fact that the aquifers are already stressed. What’s a farm to do about that?

To be continued….