Adjusting our Floating Raft Aquaponics System

When I first arrived to Taino farm the first thing I noticed about the aquaponics system was the amount of tomatoes. I had never seen tomatoes grown in a Floating Raft system and the ones growing did not look healthy, I soon realized why. Tomatoes and other fruiting plants such as cucumbers and peppers can do very well in Aquaponic systems but not in Floating Raft Systems. This is due to two reasons: root structure and nutrients available.

Floating Raft Aquaponics is the growing of plants directly in water without any media. The roots receive no support in the water that they normally have growing in the soil or another solid growing medium. Consequently, our plants relied heavily on being tied up with string that moved constantly with the wind and caused unhealthy growth. The second reason fruiting plants do not grow well in Floating Raft Aquaponics is the lack the essential macronutrients such as phosphorous and calcium. These are necessary for a plant to successfully achieve reproductive growth, producing flowers and eventually large fleshy seeds that promote new life. However, in floating raft systems these nutrients are not present because the fish solids are filtered out before the plants have access to them. The solids need to be filtered out because otherwise they would clog up the piping and fill the plant beds with dirty water that can cause root rot- a fungal infestation on the plant root that inhibits oxygen intake by the roots (which is another problem we are currently dealing with in our system).

When the solids are removed the only nutrient that is widely present in the water is dissolved ammonia produced by the gills of the fish. This ammonia is converted to Nitrite then Nitrate by the bacteria in our biofilter before it enters the plant beds. Nitrogen, in the form of Nitrate, is the promoter of healthy vegetative growth such as the stem and leaf matter of a plant. Therefore, growing plants that are harvested before they begin reproductive growth is essential for a Floating Raft Aquaponics system. Some of these leafy green plants that we are now growing instead of fruiting plants are multiple varieties of lettuce, kale and arugula, and many herbs and spices such as basil, cilantro, oregano, chives, hibiscus and mint. These kinds of plants are perfect for Floating Raft systems because they are smaller and don’t require a large root support system as well as only relying on the Nitrogen in the system and are harvested before they go to seed.

What one of our Aquaponic Floating Raft plant beds look like now:
What one of our Aquaponic Floating Raft plant beds look like now

On the other hand, we have planted many fruiting plants such as tomatoes, eggplant and peppers in our Media Beds and they are growing well. This is because there the plants grow in rocks that form support for the roots. Furthermore, we grow worms inside the rock beds that consume the solid fish waste releasing the essential nutrients that a plant needs for reproductive growth producing flowers and seeds.  

gravel media bed
What our Aquaponic Media Beds look like now