In general, new custom aquaponics systems are either based around a fixed amount of physical space or the desired volume of fish, plants or both. Designing around fish and plant production volume is far easier than designing for a specific amount of space, as each constraint changes everything about the system. You may need the help of an aquaponics or aquaculture consultant if you’re trying to design a unique system that can fit into a warehouse, fully planted greenhouse or other space with many restrictions on size and placement.

Starting with Fish or Plant Volume

You don’t need to know exactly the quantity of both fish and plants you plan to produce, but you do need at least one target number to start designing the system. Planning around plants is generally a preferred approach for many farmers because they focus more on direct sales and restaurant supply contracts and treat their fish harvests as a secondary source of income. If you prefer a system based around a high-value fish, use your stocking rates and estimated harvest numbers to determine the size and layout of the system instead.

Regardless of the projected value you choose to start with, expect to provide much more water surface for the plants in the system than the fish. In the University of Virgin Islands raft system, the plant-growing ratio to fish surface space is 7.3. Every square foot of water surface area devoted to fish raising requires over seven square feet of plant surface area downstream to make full use of the nutrients. With the proper balance among surface areas, aquaponics systems can use 97% or more of the nitrates produced by the fish. If you design a system that lacks the intermediary settling tanks and biofilters to reduce dissolved solids, you’ll have to compensate with much higher ratios of plant surface area to fish surface area.

Recirculating or Not?

After reading Chapter 7, you should have a good idea if you prefer a recirculating or decoupled system based on the benefits and drawbacks of both designs. Before starting any designs, you’ll need to pick one style or the other. Decoupled systems don’t need the same number of pumps and settling tanks as recirculating systems, so the layouts diverge significantly at one point in the design process. Switching to a different system halfway through the design, or the construction of the equipment, will increase costs and create a lot of extra work. So, make your mind up now to guide your plans properly from the start.

Basic Components

All aquaponics systems, regardless of the method you choose for the plant growing, require the same basic components:

• Rearing tanks; for fish to grow from fry or fingerlings to harvestable juvenile or adult size.
• Tanks, filters, water circulation tools, media beds and other water conditioning components; to remove dissolved solids and improve the water quality.
• Biofilter; the component that is host to the bacteria that transform ammonia into nitrites and then nitrates for the plants to absorb, which is often combined with the plant-growing troughs or beds.
• The hydroponics system; where the plants grow and the treated water is introduced, which can take many different forms.
• A sump pump; to return the filtered and treated water back to the fish (recirculating systems only).