The aquatic environment, or aquaculture system refers to the area involved with raising your fish. It is their home and should be carefully tailored to meet your fish species’ specific needs. Below, we’ll go through all your fish’s needs individually and discuss the equipment required to meet those needs. After, we’ll explore actual examples of the different equipment components.

Primary Inputs

Respiration - Air Pump
In nature, oxygen enters the water through air exchange on the water’s surface as well as through turbulence caused as the water moves through the environment.
In aquaponics, oxygen still enters the water through surface exchange and turbulence. However, primary oxygenation typically comes through mechanical air pumps. These air pumps blow air into the water through air stones, which diffuses the air into the water as tiny bubbles.

Commercial producers should consider adding pure oxygen diffusers into their aquaculture tanks. Oxygen is a major limiting factor in high-density commercial aquaculture. Studies show O2 injection can increase stocking density of fish from 0.33lb of fish per gallon with normal air to a whopping 1 lb of fish per gallon with pure oxygen injection. Recirculating Aquaculture by M.B. Timmons and J.M. Ebeling is a great resource on this topic, as well as anything to do with aquaculture.

Hydration - Water Source
Water quality is paramount to a high-functioning aquaculture system. Water testing can be done with test kits, handle-held sensors, or stationary sensors that live in the system. Your hardware needs in this category will be dictated by your purpose and goals. Commercial growers may want to invest in sensing equipment to provide them with insurance against the inevitable water quality degradation. Teachers can also use sensors to show students how this important technology works. 

Educational users also receive benefits from showing the students how to use colorimetric test kits. Residential growers can utilize simple test kits, but may want to use sensors for the ease of use, cool factor, and ability to contribute data to meaningful research projects.

Nutrition - Fish Food
Fish nutrition is provided by the fish food, which is covered in the section on the Aquaculture Success Cycle.

Automatic feeders can be installed to ensure fish are fed reliably, at the same time, and the same amount every time. These feeders are used in commercial and educational operations most extensively. Commercial growers need to guarantee their feeding schedule. Teachers don’t want to come in on the weekend to feed the fish!

Shelter - The Fish Tank
The fish tanks are perhaps the most fundamental component of the aquaculture system aspect of the Trifecta. The professional term for fish tanks in aquaculture is culture or rearing tanks

Tank Shape
Most people are familiar with the small rectangular tanks ranging from 10 to 150 gallons. Many backyard aquapioneers have used square IBC tanks to great effect, ourselves included. That being said, round tanks are recommended whenever possible, especially at commercial scale aquaculture production. Waste material builds up in the corners of non-round tanks and creates anaerobic zones that can foster disease and pestilence. Non-commercial growers only require the occasional system cleaning, but commercial farmers cannot risk any disruption and must hold regularly scheduled system cleans.

Inlet Flows - Water Pump
New Water Entering the System
Culture tanks periodically require water to be added to replace the water that evaporates or is absorbed by the plants. A simple hose will do for some growers, but commercially active growers may want to hook their system up to a water line. Systems attached to running water can automatically add water when water drops below a certain level. 

Most city water contains chlorine, chloramine, and fluoride, which can be harmful to your system health. You don’t want to add chlorine to your system and kill your nitrifying bacteria! We strongly urge you to consider using a filtration system of some sort on your water inflow. Simple carbon filters that attach to a hose can be found on Amazon. Commercial growers will require more advanced equipment and protocols like a reverse osmosis filtration system and re-mineralization system.

Recirculating Water
In aquaponics, water is recirculated from the plant beds back to the fish tank. This water typically returns to the fish tank by pump after moving through the entire hydroponic system.

Outlet Flows - Water Pump / Gravity
Culture tanks can have many types of outflows, or exits for the water to leave the tank.

The goal is to remove as much solid waste as possible from the water while providing adequate flow to the rest of the system.
Our favorite style is the SLO or solids lift overflow. Here is a great resource. As solids tend to collect towards the center of the tank. This outflow is designed to pull them up and out of the fish tank.

Another method is the Cornell Dual-Drain. One exit is drilled into the side of the tank, which sets the water height. The second exit is at the bottom center of the tank and is used to pull solids out of the system. This style is typically reserved for cone bottom tanks that help collect waste for the bottom exit. A rule of thumb for this style is that ~20% of the water should exit through the center drain and ~80% should exit through the sidewall outlet.

Temperature - Heater
Temperature is vital for keeping your fish happy and comfortable. This is done with heaters or coolers, depending on where you are growing. Indoor growers will likely have to cool their system because grow lights create a very hot environment.

Since you have already diligently picked out your fish and plant species in the Software section, you will know the temperature range for your fish. Combine this with your decision on a size for your system to help decide on your heater requirements. Remember, you will need to heat the total volume of your system to the temperature range of your fish and plants, not just the volume of the fish tank.

Space - Stocking Your Fish Tank
Stocking Density is one of the most important questions you must ask yourself. The total mass of fish that can be stocked in your tank dictates the number of fish and their size, which defines the feeding rates, which then dictates every other individual engineering system in an aquaculture system. Stocking density per unit volume depends on fish species and size. Timmons and Ebeling provide an equation to help determine stocking density.

D density = (L / C density) 

Density in lbs/ft3 = Length of fish in inches / Constant for specific fish
Tilapia: 1.5

Trout: 2
Perch: 2.5
Hybrid Striped Bass: 2.8

Flow Rate
Fish need exercise to be strong and healthy! Water velocities of 0.5-2.0 body lengths per second are noted as the optimal range for most fish. So for a full grown 12” tilapia, that is two feet per minute, or 120 feet per hour of flow velocity.
In our experience, it is optimal to turn the total volume of the fish tank over at least once per hour. So a 1000 gallon fish tank would need the equivalent of at least a 1000 gallon per hour pump running into it. Faster is fine but do not exceed the 2 body lengths per second rule noted above.

Equipment

Now that you have a general understanding of the equipment that is required to fulfil all of your fishy friends’ needs, let’s take a look at how they all fit together. 

The aquaculture system receives clean water from the sump tank, the term for the lowest point in the system. The sump tank typically immediately follows the hydroponics system and is sometimes a part of this system. The fish add ammonia to the water while it is in the culture tanks with them. Then ammonia laden water exits the culture tank through the outlets into the filtration system.

Below is a list of all the main equipment and components that go into the aquaculture system. This is not a comprehensive list and should serve as a guide and reference tool, not as an edict.

Fish Tank
Inlet
This is the return pipe from the sump tank via the pump. Try to angle it in such a way as to create a rotational flow in the fish tank. This helps give the fish a flow to swim against for exercise. It also helps swirl the solids into the center of the tank for collection by the outlet.

Outlet
SLO, Dual-Drain, Standpipe, etc. You will have to decide which type of outlet is right for your situation. At the scales we have personally worked with the most (medium to small), we prefer SLO outlets because they are simple, easily maintained, and only require cutting one hole in the fish tank. After all, why cut more holes in a water-holding vessel than is absolutely necessary?

Are you just doing a small system using a standard aquarium? All you need is a standard aquarium pump in your fish tank! This is one of the few times you would include the water pump inside your fish tank. The only other time this would happen is if your fish tank is acting as the sump tank, the lowest point in your system.

Air Pump
Smaller air pumps are rated by the aquarium volume range they can accommodate. Larger air pumps like regenerative blowers, look and sound like turbine engines. Regenerative blowers are great because they are very low-maintenance and can infuse air into water even at higher pressures. These pumps are measured in charts plotting flow rate (cubic feet per minute) versus pressure (square inches of water). As your airstones go deeper and deeper, they are under more water pressure. Regenerative blowers can infuse an area even at depths of over eight feet.

Lay out your Aeration system
Air pumps are connected to air stones via tubing. Tubing size depends on the size of your air pump. Small pumps easily connect to small air stones with standard air tubing (3/16” inner diameter).

Larger systems will need to calculate their total air needs. Gas transfer equations are beyond the scope of this document. We recommend Recirculating Aquaculture Third Edition by M.B. Timmons and J.M. Ebeling. Once you decide how much air you need, decide on how many air stones you will use and where you will place them. Typically, a PVC pipe structure connects to the air pump directly. Then air stones are piped into the PVC structure with air tubing.

Heaters
Heaters come in drop-in, submersible, and inline styles.

Drop-in heaters are not recommended because they require a steady water level and cannot be fully submerged. In our experience, they are not worth the fuss.

Submersible heaters are great for small to medium size systems.
They range from small 50 watt heaters to larger 300w aquarium heaters up to 500w titanium heaters

Inline heaters are capable of producing far more heat than a simple submersible heater. They are called inline because they are literally a heater within a pipe that is placed in the return line after the pump. These heaters usually require a specific flow threshold to become active, so they are best suited for larger systems with larger pumps. Our first inline heater was an old heater from a jacuzzi! 

Take the time to properly engineer your aquaculture system, even if you are just doing a small desktop or cabinet system. Match your equipment to your fishes’ needs and they will thrive. Keeping your fish happy and healthy will ensure that they produce ample fertilizer for the microbes and plants in your system.

Read about Aquaculture and Fish Consumables here.

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