How an Aquaponics System Works

Discover the aquaponics system of food production that involves a symbiotic relationship between plant and animal.

| January/February 2017

In recent years, there has been resurgence toward an alternative form of agriculture known as aquaponics. While the fundamentals of these systems can be traced back to ancient times, the advent of the Internet sparked a large community of do-it-yourselfers who have adapted surplus tanks and equipment into home-based systems.

What people find most appealing about aquaponics is the symbiotic relationship between plants and animals. While this happens around us every day, aquaponic systems provide a great way to view this in real time. In its most elementary form, aquaponics consists of raising plants in nutrient-rich water provided from a source that houses aquatic species, fish being the most popular. Oftentimes, though, the most important organism of the system, beneficial bacteria, is overlooked. Before we delve into the science, we need to first examine the two major systems that make up aquaponics: hydroponics and aquaculture.

Terminology and methods

“Hydroponics” is the production of crops in a nutrient-rich solution. While there are a number of methods in which to cultivate hydroponic crops, the most popular used in aquaponics include media beds, deep water culture (DWC), and nutrient film technique (NFT). Oftentimes a combination of two or more methods may be employed into one system. The choice of which method to use is often dependent upon an individual’s skill level, available time, and financial resources. However, it’s important to note that crop selection should be taken into consideration when deciding upon the method that is right for you. Additional considerations include: media beds should flood and drain at least twice per hour; a 1/2- to 3/4-inch non-limestone gravel can be used for media; a DWC system needs at least 8 inches of water depth and aeration to function properly; and an NFT system should be adjusted to allow for proper drainage from NFT channels.

Nutrients for hydroponic systems are commonly supplied via commercial nutrient concentrates. In an “aquaponics” system, these nutrients are derived from the breakdown of fish waste and nitrification. Aquaponically grown plants require the same macronutrients and micronutrients that their terrestrial-grown counterparts require.

One of the most important parameters to monitor is pH. Nutrient uptake of plants in an aquaponic system relies heavily on proper pH. A range of 6.8 to 7.0 provides the best common ground for plants, bacteria, and fish.

A requirement often overlooked when switching from soil-grown crops to aquaponics is oxygen in the root zone. The delivery method of oxygen depends upon the growing method and delivery of the nutrient-rich solution. When using media beds, the oxygen is supplied by air, which is pulled into the media as the solution drains. If using DWC, the air is provided via air stones submerged in the solution. NFT allows the top of the root mass to be exposed to air, while the remaining roots are submerged in a thin layer of nutrients.

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