Welcome to Aquaponics 101 – Other Configurations. While the focus of this series of articles is on home hobby aquaponics systems and media bed based systems, it is worthwhile to discuss the other configurations often found in aquaponics systems It is important to understand how these types of systems operate and where they fit into an aquaponics system as a whole.
We don’t mean to imply that a home aquaponics system can’t or shouldn’t employ these other system types. Given space and the time, there is no reason that a hobby operator can not successfully implement any or all of these system types into their aquaponics system.
Aquaponics 101 – Other Configurations – Nutrient Film Technology (NFT)
NFT systems are carryovers from hydroponics. The basic configuration is a trough or channel through which a small flow of water is maintained constantly. Plants rest in the cover, or an opening in the channel in net pots and the roots extend into the channel and remain in contact with the flow of water. The bacteria which convert the ammonia into nitrates exist as a film on the inside of the channel where the plant roots have access to the nutrients.
The technology is relatively simple to implement. 4” PVC drain, waste and vent pipe, drilled with an appropriate size hole, makes a quite functional NFT grow system. These can be arranged in tiers to extend the growing area vertically. The vertical arrangement makes NFT systems efficient in the use of space.
The Down Sides
NFT systems tend to require more plumbing and valves than a media bed system. This can add to the cost of the initial installation and adds maintenance time and cost. NFT systems don’t lend themselves well to growing tall or vining plants due to the lack of support at the root system.
There are several downsides to NFT systems for the small hobby operator. The maintenance of the system can become burdensome. NFT systems are also extremely sensitive to water flow. A pump or plumbing failure that goes undetected for even a few hours can mean the loss of an entire crop. Once water flow is interrupted or blocked in one of the channels, almost immediately the bacteria begin to die and the roots of the plants begin to stress. More than a few hours of no water will do unrecoverable damage to the plants in the system.
Aquaponics systems which are dedicated to NFT operations also require a higher level of filtration. This often requires that swirl filters, radial flow filters or some other type of mechanical filtration be included in the design to trap and remove the heavier and larger solid materials before they enter the troughs.
Aquaponics 101 Other Configurations – Deep Water Culture (DWC)
More commonly known as raft systems, DWC is a system that employs troughs through which water flows. The plants are rooted in net pots inserted into foam rafts which float on the water in the troughs. These types of systems are the most prevalent found in commercial aquaponics systems. They offer several advantages to the commercial grower.
First is the ease of planting and harvesting. Most commercial operators grow huge amounts of leafy vegetables in these types of system. Planting is as easy as dropping a net pot with a seedling into a hole in a foam raft. Harvesting is the reverse, pull the net pot containing the mature plant from the raft and take it to the preparation and packaging area. The raft is then recycled and reused, ready for the next set of seedlings to be inserted and floated in the trough.
Two factors are critical in operating DWC systems. One is water flow. The water flow must be consistent and great enough to deliver the required nutrient to the plants the entire length of the trough. The other factor is aeration. The plants depend on the dissolved oxygen content in the water to survive. These means that constant aeration of the water in the system, especially in the troughs, must be maintained at all times. To successfully operate a DWC system requires not only the building of the troughs and rafts but also pumps sufficiently large enough to handle the flow requirements and the installation of an air supply system that can deliver enough volume of air to maintain the required dissolved oxygen levels.
DWC systems are probably the most efficient and cost-effective method of growing plants in an aquaponics system. However, they do not lend themselves well to tall or vining plants which limits the varieties of plants and vegetables that can be cultivated.
DWC systems like NFT systems require additional filtration to keep heavy solid from collecting in the troughs beneath the rafts. Allowing this material to settle out in the troughs will result in heavy sludge build-up, which will eventually go anaerobic and begin to affect water quality.
Aquaponics 101 – Other Configurations Vertical Grow Systems
There are several vertical grow systems on the market. Many can be replicated by the handy do it yourselfer with a little work. The advantage of these systems is the ability to maximize production per square foot. Some of these systems will allow you to grow 6 to 8 plants in a single square foot of floor space. This is accomplished by planting into containers that stand erect and have grow pockets arranged around the structure from top to bottom. Nutrient water is pumped to the top of these towers and allowed to flow down through the tower, feeding the plants.
Problems and Costs
Vertical grow systems are a type of NFT system. They share the same problems and advantages. Because they depend on emitters at the top of the grow systems to regulate the flow of water down the tower, they are especially susceptible to clogging by debris in the nutrient water. This requires a much higher level of mechanical filtration, which adds cost and maintenance issues.
The grow towers are usually configured with some type of media inside the tower into which the plants are inserted. Some use a woven plastic material while others are designed to use some natural material such as coconut coir. Regardless, this media must be changed or cleaned regularly to maintain the system.
Aeroponics is a relatively new entry into the realm of aquaponics. Typically, aeroponic systems utilize some type of vertical grow structure much like the vertical grow systems described earlier. However, instead of having media inside the towers, the plants are rooted into small net pots that rest in specially designed inserts in the tower and a series of fine misting nozzles are arranged inside the tower. Periodically water is pumped through these misting nozzles inside the grow tower to deliver the nutrient solution to the plant roots.
Filter, filter, filter
I hope that you can already see the problems that can be associated with aeroponic systems. Another level of fail points is added to the system in the form of timers, additional pumps, and misting nozzles. Timers and pumps are all mechanical devices which will eventually fail. Aeroponic systems are extremely sensitive to such failures. Plants can begin to wither after only one missed cycle of water mist. The nozzles that produce the very fine mist are subject to clogging easily. This raises the level of filtration needed to keep the system operational. Mechanical filters capable of consistently removing this fine level of suspended matter in the water are expensive both to purchase and to maintain.
There are as many other variations on the types of systems described here. Many operators combine two or more of these types into their aquaponics system quite successfully. Our focus is on the hobby operator. As we continue in later articles, the majority of the discussion will be about media bed based systems. However, where appropriate, we will discuss the application, operation, and maintenance of the other systems as well.
Coming up we will take a look at the design of a home hobby aquaponics system built from a 275-gallon IBC tote.
Forward to Aquaponics 101 – The IBC Tote System ->