System design may appear to be confusing, even overwhelming. Remember though, that there is really no real wrong way to design and implement an aquaponics system. The best advice is “Keep It Simple”. Ideally, less moving parts, less energy usage, and less complexity mean less expense, less work and less potential problems!
As you work your selection process, you will likely encounter a number of new terms. Most of these terms and the vocabulary relating to Aquaponics design deal with the method used to deliver or apply water from the aquatic tank to the grow bed and its return.
Remember that there are basically 2 design types currently popular in aquaponics systems. They are raft type systems and media based systems. Most constructed aquaponics systems consists of 5 groups of components: fish tank(s); grow bed(s); plumbing and fitting(s); optional sump tank(s); optional monitor and control system(s).
Regardless of the design, an aquponics system must satisfy 4 key elements if success is to be had. These key elements include:
1) adequate water, circulation and aeration for the aquatic life 2) adequate support, water, nutrients, and aeration for the plants 3) adequate surface area, water, aeration and dark for the bio-filter bacteria 4) a means of adequate solids filtration that will not deplete the rest of the system of dissolved oxygen or cause the build up of negative compounds.
While design choice is a function of many criteria, if ease and reliability are primary concerns, the flood and drain media based system may be the best choice. It is the easiest and most reliable of the various systems, and it very low in maintenance requirements. These points generally make flood and drain systems the best choice for a home aquaponics system. This is particularly significant for the beginner.
Regardless of system choice, it should strive to maintain a balance between the needs of the aquatic life and the plants, with minimal or no need for externally applied nutrients, fertilizer or other additives.
Determining Your System Design
Popular Design Choices
There are two primary aquaponics growing methods widely in use today: media based and raft based systems. Water supplied in these systems is provided as continuous flow or as some variation of flood and drain.
Media Based Systems
Media Based Systems utilize an inert, ph balanced growing media in its grow beds. Water is either continuously moved through the grow bed(s) or is periodically introduced on a timed or flood and drain cycle. The bed is filled to a desired level, then emptied of water, which is returned to the fish tank or a sump well. Beneficial bacteria and possibly worms, break down fish effluent. As a result, both solid waste and bio-filtration occur in the media bed. Most of these systems require no added filtration, a benefit that makes them ideal for home or small group use. Media based systems are typically described as constant flow, flood and drain, or ebb and Flow systems, possibly also being further categorized as CHFIT PIST (Constant Height in Fish Tank Pump in Sump Tank), CHOP (Constant Height One Pump), CHOP2 (a variation of CHOP), and Sump Tank Two Pump.
Media Based Continuous Flow Systems, deliver nutrients to the grow bed by a form of distribution grid. The distribution grid typically consists of PVC piping with small holes drilled at regular intervals to facilitate even distribution of the nutrient enriched water. The water trickels down through the grow media, draining through the bottom of the grow bed , returning to the aquatic life tank to be once again enriched and redistributed to the grow bed(s). Even distribution of water is essential. Without it, dry areas may develop, resulting in poor or irregular plant growth. Though continuous flow is very easy to set up and operate, indications are that it does not deliver optimum plant growth in a media based grow bed system.
Flood and Drain and Ebb and Flow Systems flood the grow bed(s) in timed intervals, then drain using either a timed shut of the pump, a siphon mechanism, or other intermittent drain device. The alternate flood and drain cycle ensure equal dispersion of nutrients and enables worm and bacteria beneficial areation (oxygenation) of the beds.
Ebb and flowsystems differ from other flood and drain systems in that the water is pump up through the bottom of the grow bed(s) until it reaches a desired height. At that point, pumping is halted and the water drains back through the pump.
Flood and drain systems offer three significant advantages: 1) they provide ample oxygen to plant roots; 2) they provide effective bio-filtration for the system, and; 3) They provide a dry period for roots, which many plants prefer. Disadvantages include: 1) Water Level fluctuation without addition design innovation; 2) potentially exaggerated variations in water temperature. This latter results from media to air interface ratio that is greater than the media to water interface ratio (the grow bed dry times are longer than the wet times).
Because water level variations may adversely affect on aquatic life due to invoked stress, design variations may be a sound consideration. The goal of these variations is to reduce the stress t aquatic life by maintaining a constant water volume/height in the tank. The variations most often used involve the introduction of a sump tank to buffer variations in water volume/height in the aquatic life tank. Popular deigns include: CHIFT PIST (Constant Height In Fish Tank Pump In Sump Tank), CHOP (Constant Height One Pump) and CHOP2( ), and Sump Tank Two Pump.
In aCHIFT PIST (Constant Height In Fish Tank Pump In Sump Tank) system a sump tank is installed and the pump is placed there instead of the fish tank. Water is pumped from the sump into the fish tank, then runs out through an overflow pipe into the grow bed. It then empties back into the sump. Because the water is pumped from the sump into to the tank and an overflow causes it to empty into the grow bed(s), the water level in the tank is maintained at a constant level. In more space efficient designs the sump is located under the grow bed(s) it supports. The top of the fish tank must be high enough to allow installation of an overflow pipe necessary to direct water into the grow bed(s). Because the weight water is significant, tanks require sturdy support whether that are placed directly on the ground or on framework above it.
CHOP and CHOP2 (Constant Height One Pump) systems are both basically variations in differentiated by flow path of the water. A CHOP system normally assumes water is pumped from the sump tank to the aquatic life tank, then drains into the grow bed(s) which finally drain back into the sump. The CHOP2simultaneously pumps water from the sump into both the aquatic life tank and the grow bed(s), which then drain back into the sump.
A Sump Tank Two Pump system introduces a second pump to be used in a sump tank while the first pump is placed in the aquatic life tank. Water flow in this system begins in the aquatic life tank. Water is pumped from that tank to the beds. From there it drains into the sump tank. The second pump, in the sump tank, is controlled by a float valve. When the water in the sump tank reaches a pre-determined level the pump turns on and water is pumped back into the fish tank. This design opens the system to the danger of pump failure and sump tank overflow.
Raft Based Systems
Raft based systems, for the most part, utilize no grow media other than nutrient rich water to sustain crop growth. Raft systems are basically continuous flow systems, in which water continuously washes roots with nutrients, then moves through filtration back to aquatic life tanks, where they incorporate more nutrients from the fish. They typically use foam rafts floating in a channel filled with fish effluent water that has been filtered to remove solid wastes. Plants placed in holes in the raft hang freely in the water, extracting the nutrients which they need. Raft type systems are most commonly found in commercial operations. These systems are typically classified as either deep water cultures (DWC) or a variation of continuous flow water only systems called nutrient film technique (NFT) systems.
DWC (Deep Water Culture) is most referred to when discussing raft systems operate in manner in which plants grow while suspended over a tank of nutrient rich water flows with supplemental aeration. In most DWC systems mechanical filtration must occur before fish water is sent to the raft area of the system. DWCis most often restricted to low-growing, leafy plants such as salad leaves or herbs because larger and more weighty plants contribute to platform instability.
NFT (Nutrient Film Technique)utilizes a techniques in which plant roots are suspended into a channel in which a thin and even film of aerated nutrient solution flows. As is true with DWC, in fact more so, filtration is critical. Unfiltered and incompletely processed fish waste in the trough and on roots will negatively impact the plant growth. For this reason, NFT systems require separate, effective solids and bio-filtration. Thin film water delivery systems are also susceptible to greater temperature and water quality fluctuations in short periods of time. These systems don’t usually have the weight support ot space to properly accommodate many plant root systems. So they are typically restricted to use in salad leaf plants.
By the nature of their operation, these systems are Continuous Flow Systems, delivering the water to the grow bed continuously.