Over the past few weeks, we’ve been busy here at CVI with the fish ponds. I feel like I’m more of a fish farmer than an engineer now! We started off with draining one of the big ponds and harvesting all its fish. It was so exciting to see what I’d been talking about for weeks actually materialize! It was a tiring, muddy day but so worth it.
CVI hired a bunch of community guys as day laborers, and they started by unearthing the pipe and digging a drainage ditch. Once the pipe cover was removed, water gushed out! To drain even faster, we also pumped water from the pond with the petrol pump. Then it was time to get some fish! Pairs of guys hopped in the water and dragged mosquito nets along the length of the pond trying to catch as many fish as possible. It’s harder than it sounds—those fish are pretty smart and very fast! When they made it to the far side, we’d take the nets and sort the fish. The big ones we kept for eating, and the small ones we threw into the other two ponds. There were some big ones, but a lot of the fish were quite small because a wild strain of tilapia has invaded the ponds. The red tailed fish are male, and they grow well. The white bellied fish are the females of the same strain, but the fish with black stripes are like weeds that invade the population and don’t grow well. Unfortunately, we had a lot of black-striped tilapia.
As the water drained, it became a race against the clock to capture all the fish before the pond went dry. Everyone jumped in and tried to grab fish! Some held a long black netting and walked it across the length of the pond to corral the fish while the rest of us tried to capture them with nets and our bare hands—they were fast, and their fins were spiky! They were hard to catch with your hands! Soon all the water drained from the corners of the pond leaving fish flapping in the mud. We waded through the ankle deep muck trying to scoop up the critters before they suffocated.
Finally, most of the fish were captured, and we prepared to enjoy our labor! Tracey, the catering class teacher, and some of the girls cleaned and gutted fish and began frying them in oil. They were really tasty! I learned that you start by eating the hard tail of the fish and continue down all the way to the eyeball, which wasn’t as bad as I was expecting. :)
The community guys began digging out all the mud on the bottom of the pond. This pond sludge comprised of rotting organic matter needs to be removed because it creates an oxygen sealing layer that prevents good bacteria from growing on the bottom and instead promotes anaerobic bacteria which release toxic hydrogen sulfide. After removing the sludge, we limed the pond to sterilize it and kill any pests before restocking. Before adding water though, we sloped the sides of the pond at a 45° angle. The sloped sides help prevent erosion because waves roll up the sides rather than crash into a blunt edge. We also covered one of the sides with a plastic liner and mud-filled bags because that side leaks water during dry season. Finally, we started pumping water back into the pond! With the help of the District Fisheries Officer, we located a fish supplier with good strains, so when CVI reopens after the Christmas break, we’ll be ready to restock the pond with healthy, fast-growing tilapia! We’re also going to get some catfish that will eat the stunted tilapia we already have that won’t grow.
One form of aquaponics is growing plants on rafts, so one day, Knight, the head plant farmer, and I tried an experiment. In the US, people usually use Styrofoam insulation board for rafts, but that’s expensive in Uganda and only available in the capital of Kampala. Instead, we tried to make a raft out of locally available materials. One rainy day I was staring at the grass roofs of our huts and had an inspiration, “Dried grass floats!” So Knight cut some long grass and let it dry for a couple days then we attempted to make a raft. Neither of us had any idea what we were doing, so we made it up as we went. We tried gathering small bundles of grass and tying them together—it held together; we just hoped it would float!
Normally, the aquaponic rafts are in a separate bed from the fish, but since this was just an experiment, we were going to put our raft in a fish pond. I knew the fish would eat the plants’ roots, so I asked Knight if there was any thin cloth or mesh we could use to protect the roots. She said, “a mosquito net!” So she grabbed an old net, and we figured out how to attach it to our raft. Finally, we were ready to test our contraption! We laid it in the water and held our breath—it floated! We stuck some collards, tomatoes, and peppers between the grass bundles and prayed our raft would last overnight.
This raft experiment perfectly portrays my experience designing an aquaponic system in Uganda. Some days are filled with excitement and anticipation as I make progress while other days are filled with disappointment as I go back to the drawing board and question if I can even build an aquaponic system. Usually I feel like I have no idea what I’m doing—my limited experience helping with an aquaponic system for a year at university didn’t prepare me to design a whole system by myself. I’m an engineer—I don’t know fish and plants! So I read as much as I can online when I get Internet, contact experts, and ask the CVI farmers questions to figure out how to adapt complex aquaponics to rural Uganda. It’s a journey of ups and downs, but whenever I grow discouraged, I only have to listen to the girls’ heartfelt songs during nightly prayers to remember that God called me here for a purpose and He will give me the strength and skill to accomplish His plan.