Every now and then, the writer of this column receives messages from students asking if they can visit a backyard aquaponics farm. Their requests are accommodated — as much as possible — provided that schedule permits. The latest visitors were from Polytechnic University of the Philippines (PUP).
There were three of them, led by their team leader Joshua How. Interestingly, when asked if they’re interest in aquaponics was for a school project, they replied both yes and no. Yes, it was for a project. No, it wasn’t for school. And this got this writer curious since a lot of students tend to do work only because it is required for school.
As it turns out, the students were learning as much as they can about aquaponics because they were in the process of building a system for their church. They wanted to grow fresh and clean food for their community. Now that’s definitely a worthy cause.
We then discussed design, construction, and operation problems that often come into play for first-timers. It was a fruitful exchange because key lessons were passed on as to how beginner mistakes can be avoided. For example, they thought about using concrete tanks but decided not to when — during the workshop they attended last 1 February — they found out that concrete tanks will likely have a substantial impact on the pH of the system. The advance information saved them from wasted time, effort and resources.
Next on their list was the utilization of media beds which has been more of the go-to design for backyard setups compared to Deep Water Culture (DWC) systems. The issue about media clogging fast, however, made them re-think the adoption of this design. To stress the point, this writer showed them a media bed full of pumice rocks that were already overwhelmed with solids buildup. There’s a load bearing capacity limit that must be considered.
This lesson was a strong reminder about considering operations and long-term maintenance before a design is chosen and actually built.
How the re-mineralization tank works was also demonstrated. The aerators were turned off, solids were then allowed to settle at the bottom, the clearer water at the top portion of the tank was then drained, and that nutrient-rich water was introduced to the system. The radial flow filter was then partially drained (to refill the re-mineralization tank with solids-filled-water) and the aerators turned on again. This is how the minerals in fish waste are further biologically processed to make them available for plants to absorb.
Next in line was feeding the fish. Joshua and his friends were surprised to find out how big the fish actually were when the latter swam up to the water surface to eat the floating feeds. Stocking density, which means how much kilograms of fish per volume of water can stocked, was also reviewed. The list went on.
Before wrapping up, the wicking-bed portion of the backyard farm had sprawling stevia. This writer asked the students to taste the leaves. They were a bit hesitant at first but eventually agreed.
To their surprise, it was very sweet. They were then informed that stevia is often used as an alternative sweetener to replace regular sugar. Joshua and his friend responded that they will look into growing this plant because they had a lot of church members who were diabetic.
Thank yous were then exchanged and the students left, hopefully, better equipped as they start building their own system.