1. Introduction to Aquponics
An Integrated Fish and Plant Production System

2. Aquaculture Aquaculture -- also known as fish or shellfish
farming -- refers to the
breeding, rearing,
and harvesting of plants
and animals in all
types of water
environments including
ponds, rivers, lakes, and
the ocean.  

3. What is Hydroponics?
Hydroponics is a method of growing plants using mineral nutrient solutions, in water, without soil.

4. Aquaculture + Hydroponics = Aquaponics
What is Aquaponics?
Aquaculture + Hydroponics = Aquaponics
Combined production of fish and hydroponic plants in a recirculating aquaculture system
Aquaponics is a hybrid system linking aquaculture, in this case the production of fish, with hydroponics which is the production of plants in a soilless environment. The concept of aquaponics is a relatively new science and came about because there has been pressure to improve freshwater use and decrease nutrient discharge to adjacent environments. Aquaponics is capable of addressing both issues. The aquaponic system is a recirculating aquaculture system reusing the majority of its water volume each day and the dissolved wastes created by the fish are converted into a marketable hydroponic crop. The plants use the fish wastes as a nutrient source, therefore cleaning the water and then the water returns back to the fish in a form that is not harmful for fish production.
Managing an aquaponic system requires knowledge of both fish and plant health and production. Because there is a synergistic relationship between the fish and plants choices in management can positively or negatively affect system production. Although tilapia eat algae they will require a commercial diet for the stocking rates in the aquaponic system. This diet provides all essential nutrients for tilapia health and growth and in addition supplies the plants with 95% of the nutrients required for their growth. Also reliable energy is necessary to keep pumps and blowers running 24 hours a day throughout the year. Also the aquaponic system is an investment requiring money to operate the system until the production of plants and fish are ready for market and sales occur.

6. Why Aquaponics? Advantages Disadvantages
Plants use nutrients from fish waste to produce a marketable product
Hydroponic plants act as biofilter
Integrated systems reuse nutrients and conserve water (up to 98% less water than conventional farming)
Disadvantages
Requires knowledge of fish and plant husbandry
Requires commercial fish diet and reliable energy source
Moderate initial capital costs for system construction

8. Tilapia production Stocking and Harvesting Staggered production
Drain and harvest tank 24 weeks later
Average weight 700 – 750 grams/fish
Survival greater than 95%
Staggered production
Allows a tilapia harvest every 6 weeks
A total of 2 harvests from each tank/year
For the aquaponic system the management strategy for tilapia production is to stagger the fish production tanks. Staggered production is a benefit because it results in regular harvests for market, but relies on a consistent supply of tilapia fingerlings. The staggered production also creates a steady supply of nutrients for the hydroponic plants. Throughout the year the nutrient concentration remains relatively stable because the fish are at different stages of production. Every six weeks a specific tank in the system is harvested and restocked with fingerlings. Over a one-year period each tank is harvested twice. The fish stocked into the tank are sex-reversed at a young age to produce male fingerlings. Male tilapia are preferred because they grow faster than females and single sex populations prevent reproduction from occurring in the system. After 24 weeks in the tank the fish are harvested with a final individual weight of approximately 1.5 pounds and a survival rate greater than 95%. Towards final harvest fish biomass can approach 0.5 lbs/gallon.
We use a 32% protein tilapia diet and feed it to the fish 3 times each day. Our feeding method is called ad libitum, which is a fancy way of saying we feed the fish all they will eat within a 30 minute time period at each feeding. A common Feed Conversion Ratio (FCR) for our aquaponic system is The KEY concept for the aquaponic system is maintaining a proper ratio of the tilapia feeding rate to hydroponic growing area. We recommend 60 – 100 grams of tilapia feed/m2 of hydroponic growing area/day. This equates to approximately lbs of feed/day for the entire system. Small experiments have shown a feeding rate of up to 180 grams of feed/m2 of hydroponic growing area/day is possible, but 60 – 100 grams minimizes concerns with water quality management.
Also each fish tank contains 22 airstones which allow atmospheric air, the same air you and I breath, to enter the tank and provide sufficient oxygen for the fish. The air is pushed into the system by a 1.5 Horsepower regenerative blower.

9. What do fish need? Aeration-Fish are animals and need oxygen
Food-Feed a floating diet with 32% protein 3 times/day
Achieve daily feeding rate of 60 – 100 grams of diet/m2 of hydroponic growing area/day
This is optimal amount for plant production, balances the system, and minimizes water quality problems
Aeration-Fish are animals and need oxygen
Several airstones/tank
Pump to circulate water
Clean Water-Fish can’t be left to float in their wastes.
They emit ammonia from their gills and create solid and liquids waste filled with ammonia

10. Marketable Nile tilapia
Tilapia Production
Here is a photo of a market size Nile tilapia that weighs approximately 1.5 pounds and measures inches in length. The picture to the right shows how the feed floats once it is added to the tank. This allows the farmer to observe the fish eating the feed. If they don’t finish all the feed in a 30 minute period the farmer will want to decrease the next feeding accordingly. If they finish all the feed within a 30 minute feeding the farmer will want to bump the feeding rate up a little. A general rule of thumb is if the fish finish all the feed within a 30 minute feeding then the water quality and fish health is good. If the fish do not consistently finish the feed over 3-4 consecutive feeding periods then feeding should cease and water quality and fish health should be checked.
Marketable Nile tilapia
Feeding a Fish Tank

11. Plant Requirements Light Adequate Spacing Oxygen Crop Dependent
Temperature
Protection
Indoor production is climate controlled
Wind protection
Outdoor production is dependent on the season
Control of pests
Now I am going to cover some of the very basic requirements your hydroponic plants will need. First of all is light. Plants require adequate natural lighting or artificial lighting for proper growth. Plant roots require oxygen. If the area they are grown in lacks sufficient oxygen then the roots will die and the crop is lost. Temperature is important. Just like any biological organism plants require the proper temperature. If plants are produced indoors then ventilation or heating will be required. Outdoor production is dependent on the ambient air temperature just like traditional horticulture. Depending on the crop, spacing is important to reduce competition for light and allow air movement. Also protection from wind and monitoring the plants for pests are important for plant health and production.

12. Plant Requirements
There are 16 essential macronutrients and micronutrients for plant growth
Macronutrients
N, P, K,
Micronutrients
Ca, S, Mg, B, Cl, Cu, Fe, Mo, Mn, Z
There are recommended ranges for aquaponic and hydroponic vegetable production
Typically aquaponic nutrient levels are lower than recommended hydroponic nutrient levels
Possible because fish are always creating effluent that passes through hydroponic raceways
Regarding nutrients there are 16 essential nutrients plants require. The actual concentration will be different depending on the type of plant produced, nonetheless, a plant requires the macronutrients Nitrogen, Phosphorus, Potassium, Calcium, Sulfur and Magnesium and micronutrients Boron, Chloride, Copper, Iron, Molybdenum, Manganese and Zinc.
If you were to speak with a hydroponic producer and aquaponic producer you would soon see that the recommended ranges for the hydroponic plants are quite different. In hydroponics the original nutrient solution is created and over time the macronutrient and micronutrient concentrations are reduced as the plants adsorb nutrients for growth. After a period of time the hydroponic nutrient solution must be thrown out or additional nutrients added to maintain plant growth. With aquaponics the nutrient solution is always being created for the plants. Each day we feed the fish and wastes are created. A low concentration of nutrients is always available for the plants to extract for growth.

13. Nitrogen Balance
The main nutrient that we monitor in our system is nitrogen.
There are 3 kinds of nitrogen that occur in aquatic environments:
Ammonia
Nitrite
Nitrate
We want to limit the amount of Ammonia (<1 ppm) and Nitrite (< 5 ppm)
Nitrates are not as harmful to fish and should be ppm.

14. pH Balance Must compromise pH for fish, plants and biofiltration
Fish prefer 7.5 – 8.5
Plants prefer 6.0 – 6.5
Nitrifying bacteria prefer 7.0 – 8.0
Maintain aquaponic system pH at 7.0
Calcium hydroxide [Ca(OH)2] and potassium hydroxide (KOH) increase pH when it falls below 7.0
Calcium hydroxide and potassium hydroxide added on alternate basis until pH returns to 7.0
Measuring the pH allows the farmer to determine if the culture water is ideal for the biological processes occurring in the aquaponic system. So maintaining the pH of the aquaponic system is important. Because the system contains fish plants and nitrifying bacteria, which help to convert the fish waste ammonia into nitrate, we need to meet at a middle ground for what each organism prefers. Maintaining the pH at 7.0 is optimal for fish, plants and bacteria. Due to the biological processes occurring in the system the pH will want to continuously drop below 7.0. We add calcium hydroxide and potassium hydroxide to the base addition tank to maintain the pH at 7.0. Both of these chemicals will cause an increase in pH.

15. Why is Aquaponics Better Than Hydroponics?
In Hydroponics, humans have to recreate the nutrient environment needed to grow plants.
Nutrient concentrations decline over time and have to be re-added.
In Aquaponics, the nutrients are provided and recycled through the system (i.e. fish poop).

16. Nutrient concentration for Aquaponics vs. Hydroponics
Aquaponics (mg/L)
Hydroponics (mg/L)
Calcium
10.0 – 82.0
150.0
Magnesium
0.7 – 13.0
50.0
Potassium
0.3 – 192.0
Nitrate
0.4 – 82.0
115.0
Phosphate
0.4 – 15.0
Sulfate
0.1 – 23.0
113.0
Iron
5.0
Manganese
0.5
Copper
3.0
Zinc
0.05
Molybdenum
Boron
This table compares a typical nutrient concentration between aquaponic and hydroponics. You can see the aquaponic nutrient concentration is below the recommended hydroponic concentration throughout the list. Again what is unique about aquaponics and why it works is the fact nutrients are being added to the system daily in the form of fish feed. The fish feed provides the majority of the plant nutrients. On the other hand, hydroponics begins with a high nutrient concentration and anticipates the nutrient concentration will decrease over time. After a period of time the hydroponic solution must be replaced.

17. Nutrient Supplementation
Tilapia effluent provides adequate levels of macronutrients and micronutrients, but supplementation of calcium, potassium and iron required
Calcium supplemented with addition of calcium hydroxide
Potassium supplemented with addition of potassium hydroxide
Iron supplemented with the addition of chelated iron to maintain concentration of 2 mg/L
The whole idea behind aquaponics is the fish waste provides nutrients for the hydroponic crop. In a perfect world that would be the case. The fish waste provides the majority of plant nutrients but lacks sufficient calcium, potassium and iron to sustain plant health. Therefore calcium and potassium are needed. Remember… calcium hydroxide is added to the system to maintain a pH of 7.0. When it is added to the system calcium is added, as well. We kill two birds with one stone. The same is true with potassium hydroxide seen. When added to the system to buffer pH potassium is supplemented as well. We add between 1 and 2 pounds of calcium hydroxide or potassium hydroxide to the base addition tank when needed. We alternate the addition of calcium hydroxide and potassium chloride when needed to supplement nutrients. Iron is added in a chelated form every three weeks or as needed to maintain a sufficient iron concentration. A chelated form ensures the iron is available for plant uptake and does not precipitate out of the water. Iron can be added at the degassing tank to quickly introduce it into the hydroponic troughs.

18. Plant Production Methods
Batch Culture
One planting and one harvest of aquaponic system during plant production period
Can quickly deplete nutrients as plants mature
Staggered Production
Multiple plantings and harvests on a rotational basis
Prevents quick nutrient depletion
Allows uniform nutrient uptake
There are two types of plant production methods that could be used in the aquaponic system. We call them batch culture and staggered production. With batch culture the whole hydroponic component (i.e. all the raceways) are planted at the same time with the same age seedlings. When the plants are ready for harvest, all the plants are removed from the system for market and then the whole system is replanted again. One advantage to this production technique is a large market can be supplied monthly with lettuce; however, a disadvantage is as the plant biomass peaks the nutrient concentration in the system is depleted and the potential for plant nutrient deficiencies can increase.
At UVI we recommend staggered production for most scenarios. Just like the fish production, staggered plant production allows for regular harvests on a smaller scale. This prevents nutrient depletion, but requires a good management protocol to ensure seedlings are ready for weekly transplanting.

19. Principles to Remember
Staggered fish and plant production maintains a balanced nutrient concentration in the system
Optimum fish feeding rates prevent nutrient accumulation or deficiency
Base addition maintains optimal pH and supplements nutrients
Be vigilant in preventing, recognizing and treating plant pests/disease
1) Finally here is a summary of important concepts to remember concerning the aquaponic system. Staggering your fish production allows for a constant supply of nutrients with little fluctuation in nutrient concentration; staggering your hydroponic crop production results in a steady nutrient uptake without leading to plant nutrient deficiencies.
2) Feeding the equivalent of g/m2 plant growing area/day helps to maintain a balanced system and minimizes water quality problems. This range is sufficient for both fish and plant growth and production. If you were interested in designing your own aquaponic system I would start with this simple ratio and calculate fish and plant production area based on it. I will add that if you are interested in starting an aquaponic system use the UVI design. Many of the problems have already been worked out and it will save you many headaches.
3) Cleaning your net tanks will affect the amount of nitrate in the system. For higher levels of nitrate clean twice per week and for lower levels clean once per week.
4) The addition of calcium hydroxide and potassium hydroxide when pH falls below 7.0 helps to neutralize the pH and raise it to 7.0. The addition of these bases also supplements the system with calcium and potassium which are two limiting plant nutrients that are not supplied in enough quantity solely by the fish feed.
5) Scout and keep records of when your plants were affected by certain pests and what pesticide was effective in controlling the pest population. And remember to read the pesticide label and apply the pesticide according to the directions provided.