How do you get a classroom full of distracted middle schoolers to pay attention? A 300-gallon tub of live fish helps do the trick.

In a lab on the second floor of the Adaire Alexander School in Fishtown, roughly 35 tilapia swim, splash and amuse Bill McGeehan’s seventh-graders. It takes a bunch of effort to maintain — including daily tasks like checking the pH of murky water and changing a septic tank full of, well, crap. But McGeehan said the project is more than worth it.

In tandem with helping students learn biology and environmental science in real time, the aquaponic farm has the potential to generate hundreds of pounds of food each year — which could eventually be donated to hunger nonprofits.

Aquaponics is a model that’s gaining traction worldwide, spreading from its origins as a DIY tactic into the commercial agricultural industry. The farming method uses less water than traditional systems, and has the potential to produce food on a large scale in much smaller spaces.

The aquaponics set-up in Adaire’s science lab Credit: Michaela Winberg / Billy Penn

Adaire’s installation works like this: The fish swim around and do their thing, as the poop-filled water around them is pumped out to a separate tank.

There, it fertilizes a pebble-soil mixture full of worms, the water from which is funneled into beds where floating plants are growing — tomatoes, peppers, leafy greens, you name it.

It’s a process that McGeehan hasn’t yet perfected. In the last two years, his tomatoes have come out too watery, and his arugula far too peppery. The actual peppers grown were so hot that his students instituted a grade-wide competition to see who could eat the most without needing water.

The fish- and worm-fertilized pebble-soil that’ll feed the water-grown plants Credit: Michaela Winberg / Billy Penn

“The Jalapeno pepper plant really thrived, god knows why,” McGeehan said. “They were all like, ‘I can eat it.’ And then it’s, ‘I need some water!’”

No matter the learning curve, McGeehan doesn’t mind the responsibility. He loves the waterborne one-pounders. He’s grown so affectionate toward the tilapia that without reservation, he’ll stick two fingers in the water and pet their scales.

“I love my fish,” McGeehan said. “I like taking care of them, and I really like how much I learn from managing the system.”

Council President Darrell Clarke paid the school a visit last month to check out the unique program, getting a look at the fish and peeping some basil plants in their infancy.

McGeehan thinks it’s a great learning tool — one the school district should consider implementing citywide. It took $8,000 to install the fish tank and its connected mini-aquaponics operation, he said, all of it funded by the nonprofit parents’ group Friends of Adaire.

Kids seem way more interested in science when they can see it, McGeehan explained, swimming around right in front of their eyes.

“We’re in the process of catastrophically destroying Earth’s ecosystems,” McGeehan said. “What these guys need to be able to do is focus on putting it back together.”

The final experiment comes at the end of the year, when the kids will dissect their white-gilled-friends. It’ll be a sad day in the classroom — especially for McGeehan, who raised the tilapia up from inch-long babies. But they’ve grown too big to keep inhabiting the tank without producing too much ammonia, killing themselves and the plants they’re helping grow.

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If you’re worried the students will be traumatized, slicing their pals and all, think again. Apparently they’re already getting hype.

“They’re ruthless,” McGeehan said. “They want to be involved in killing [the fish], but I’m not going to allow that.”

Next year — and every year after that — McGeehan anticipates a fresh shipment of baby fish to raise up. For now he’s sticking with tilapia, since they’re pretty hard to kill. But eventually, he hopes he’ll get good enough at managing the system that he can ask for more diverse waterborne creatures, and grow some more successful produce to stock the cafeteria.

“Maybe later years, when I get better at managing the system,” McGeehan said. “But I think we give these guys a pretty happy life while they’re here.”

Michaela Winberg is a general assignment reporter at Billy Penn. She covers LGBTQ people and culture, public spaces, and transportation and mobility. She also sometimes produces radio and web features...