Hydroponics involves growing plants in a soilless medium and essential nutrient water solutions for proper plant growth and development. This form of agriculture has been in use for thousands of years. Like plants growing in soil, plants in a hydroponics system require essential nutrients and water to flourish. Instead of getting critical nutrients from the soil, plants receive the vital nutrients for maximum growth dissolved in the water and passed over the root system.
Like hydroponics, aquaponics is another method of growing plants in nutrient-dense water without soil. However, in an aquaponic system, fish supply the nutrients through their waste instead of the grower adding the nutrients. Beneficial bacteria, colonized in the biofilter, convert the waste into valuable nutrients for plants to thrive. They convert ammonia from fish waste into nitrites then into nitrates, the primary plant nitrogen source. As the water passes through the plant roots, the plants clean the water and recycle it back to the fish tank.
The following explanations of the differences in cost, setup, and operation of the two systems can help growers decide what approach works best.
System Components and Design
System design and operating components are the most significant difference between hydroponics and aquaponics systems. The first difference between the two systems is the aquaponics system filtration (Figure 1). The filter initially captures the fish’s solids and provides a zone for nitrifying bacteria to colonize and convert the fish waste into vital nutrients for the plants.
The choice of plant growing methods is another difference. Deepwater raft and ebb and flow media systems work for the two growing systems; however, there is some difficulty utilizing nutrient film technology (NFT) for aquaponics. NFT is a practice in which very shallow water flows through channels where the plant roots hang. Due to small diameter tubing clogging frequently, NFT is problematic in aquaponics. NFT is used extensively in hydroponics and is the system of choice for most hydroponic growers (Figure 2). Construction of a hybrid system using larger tubing that does not clog easily has been successful in aquaponics.
Startup and Operating Costs
The startup costs for the two systems are similar; however, the aquaponics system involves a few more components consisting of filtration, additional aeration, and fish. Fish costs vary according to the fish selected for the system. Ultimately, these costs are comparable to the extra nutrients needed for hydroponics and can be offset by selling the fish at the end of the growing season.
The operating costs for aquaponics are generally slightly more expensive due to the additional air pumps needed to aerate the system.
Acclimation or Cycling Period
An acclimation or cycling period is necessary before each system can be fully productive. A new hydroponics system only needs the nutrient solution to cycle and stabilize before introducing plants.
An aquaponics system requires time for beneficial bacteria to develop in the filter media to create a safe environment for the fish and plants. The amount of time depends on the amount of fish waste and the water temperature in the system. It can take 6 to 8 weeks to cycle the system; however, the acclimation period can be up to 2 weeks shorter with warmer water temperatures. Daily water quality monitoring during the acclimation period is required to ensure a safe environment for the fish. Once the aquaponics system is fully acclimated and stabilized, the system can be operated at maximum capacity.
A balanced aquaponics system acts as an artificial ecosystem due to the fish, beneficial microbes, and plants. The system is sustainable because the vital nutrients are available with minimal external inputs, and few resources are necessary. Hydroponic systems, however, need the daily addition of nutrients to the growing solution as the plants deplete it.
The nutrient source requirements are entirely different between the two systems. In a hydroponics system, the manager must periodically restart new growing solutions for the plants by mixing in artificial fertilizers to create the appropriate nutrient levels (Figure 3). In an aquaponics system, the fish waste provides a natural supply of nutrients that need not be replenished. Most commercial fish food used to feed the fish offers a balanced diet and essential nutrients for adequate plant growth.
Operating Maintenance and Waste Disposal
For daily operation, much less water quality and nutrient monitoring are necessary for an aquaponics system. Water pH and ammonia levels are the most critical parameters to check weekly in an aquaponics system due to the stress these cause to fish when not maintained at the proper levels. For a hydroponic system, daily monitoring of the electroconductivity (EC), pH, and nutrient levels is necessary to keep a balanced and productive method.
Aquaponics systems generally only lose water through evaporation or during washing of the filtration unit. Therefore, an aquaponics system does not need flushing as long as the system is operating correctly. However, regularly draining a hydroponics system and refilling with fresh growing solutions is necessary to avoid nutrient build-up that may harm the plants.
Since the hydroponics system needs regular draining, dumping this nutrient-rich water into natural water bodies can affect water quality and cause algal blooms. Disposing of hydroponic wastewater in the home drain can potentially disrupt wastewater treatment plant operations. Wastewater from an aquaponics system is minimal and is safe to use as either a wet fertilizer or dried for soil-based plants.
The Final Decision
Ultimately, gardeners should choose a system based on their needs and preferences. Select the system that will bring enjoyment to growing fresh, natural food. Growing produce in soilless systems is gaining popularity. It may provide positive benefits for all gardeners, even those with disadvantages or disabilities. While aquaponics may be more sustainable than hydroponics, both systems have potential advantages over traditional gardening in soil.
For more information, see HGIC 1738, Aquaponics – The Culture of Fish and Plants Together in One System.