Welcome to our ongoing series highlighting our Aquaponics Curriculum!
Over the coming weeks, we will be posting a series of articles covering the basics of each Curriculum Topic. Today, we are covering Topic 1, Lesson 4, Hydroponc and Aquaponics Designs. Each of these blog posts is aimed to give an overview of the subject and provide one or more critical thinking questions. You can find our first post in this series here. Enjoy!
There are two categories of hydroponic systems: aggregate and non-aggregate. Non-aggregate hydroponic systems are designed to support plants with their roots hanging into the nutrient solution. Aggregate hydroponic systems use substrates to provide support for the plants. In aggregate hydroponics, the systems may be a closed or open system. An open system denotes that the system does not recycle the nutrient solution whereas a closed system does recycle the nutrient solution (non-aggregate systems are mostly closed systems).
The first non-aggregate system is the float bed (deep raft, raft, deep flow, and deep channel) system. The float bed generally uses a large piece of Styrofoam with 2 or 3 inch holes cut into it. Net pots are inserted into these holes. The net pots provide support to the plants and the Styrofoam provides the floating feature to the system in a large tub of water. An air pump outside of the tub is connected to an airstone inside the tub via plastic tubing. This setup provides the roots with air, which is necessary for growth, nutrient uptake and respiration.
Image 1: Float bed on top and sump tank on bottom.
Image 2: Net Pot
The second non-aggregate hydroponic system is called nutrient film technique (NFT). NFT systems use the same concept of having the roots in nutrient solution. Instead of plant roots suspended in a large tub, NFT has the plant roots suspended in “channels” where holes are cut on the top of the channels to allow for net pots to hold the plants. These channels are sloped so that thin layers of nutrient solution can flow through. The nutrient solution is pumped to one side of the channel and flows to the bottom of the channel by gravitational force. At the bottom of the channel, the nutrient solution collects in a sump tank that is recycled back to the top of the channels by the water pump. Unlike float bed systems, NFT systems do not allow for complete root submersion into the nutrient solution. The plant roots are fed nutrients only by a thin layer of nutrient solution, where the rest of the channel is empty space designed to allow for air flow to the roots.
The third non-aggregate hydroponic system is aeroponics. In this design, plants are suspended in net pots put in holes that are cut out of a plastic panel (similar to the float bed system and the NFT system). The roots are suspended below the plastic panel in and enclosed open space. The roots are periodically sprayed with a nutrient solution every 2-3 minutes for a few seconds to keep the roots moist. A misting system along with a timer controls the spraying times. The excess moisture from the spraying is eventually collected at the bottom of the enclosure to be re-sprayed on the roots.
The first aggregate hydroponic system is the drip system. Drip systems are the most commonly used hydroponic system. Plants are supported in substrates such as Rockwool, coco coir, rocks, etc. in an area called the media bed. In a separate container, the nutrient tank, the nutrient solution is pumped to the media bed through drip lines. Drip lines are tubes that have holes or slits to allow for the nutrient solution to drip on to the substrates near the plant rows. The media bed will be slightly sloped to allow for collection of the unused nutrient solution at one end. If the system is closed, this nutrient solution will be directed back to the nutrient tank. If the system is open, the nutrient solution will be drained out of the system.
Image 3: Media bed with overflow pipe in the middle. Black fish tank in the back.
The second aggregate hydroponic system is an ebb and flow (flood and drain) system. The ebb and flow system uses the same basic setup as the drip system. However, it does not have the drip lines. Instead, the ebb and flow system uses a submersible pump in the nutrient tank to pump nutrient solution to the media bed for an allotted time using a timer. There is an overflow pipe in the media bed that is positioned vertically. While the pump is turned on, the overflow pipe drains whatever water goes above the pipe back into the nutrient tank. This part of the design is essential so that the media bed does not over-flood. After the timer turns off the pump, the nutrient solution drains back into the nutrient tank.
The third aggregate hydroponic system is the wick system. The wick system uses a media bed and a nutrient tank similar to the drip and ebb and flow system. The wick system brings nutrient solution to the media bed by using a wick to passively transfer water and nutrients to the media bed. This system generally does not use any automated parts.
Although there are many different types of hydroponic systems, some work better than others. Additionally, these systems can be connected to a fish tank instead of a nutrient tank which qualifies it as an aquaponics system. The most popular hydroponic systems that can be converted to aquaponic systems are the float bed, ebb and flow and NFT systems.
Critical Thinking Question
In which systems would a power outage be dangerous for the plants?