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Project Objectives:


The California Native Garden Foundation (CNGF) is in need of a functional aquaponics system so that Middlebrook Gardens may be used as an educational space for students this coming summer season to teach awareness of a more just and sustainable world. 
The project objectives are as follows:

  1. Design a functioning aquaponics system that: a) successfully grows a variety of plants, b) has enough water flow to minimize algae growth, and c) supports plants that intake enough fertilizer to minimize algae growth

  2. Create a sustainable aquaponics system that lasts as long as possible with deteriorating and negatively impacting both the plants and the fish

  3. Implement a system with an educational aspect in mind both a) incorporating signs to differentiate the purpose of each system part and b) implementing simplicity so that every major design aspect is visible

In-depth Problem Definition:

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  1. Working aquaponics system

    1. The product must be efficient and successfully grow a variety of plants

    2. The product must have enough water flow to minimize algae growth

    3. The product must support plants that intake enough of the fertilizer to minimize algae growth

  2. Sustainable aquaponics system

    1. The product should last as long as possible without deteriorating and negatively impacting the plants

  3. System must be designed with an educational aspect in mind

    1. The product could incorporate signs to differentiate the purpose of each system part/piece

    2. The product should be simple and clear enough to see all important parts/elements within the system

  4. The product must be done or have an iteration prototype by the end of the quarter
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Fluid Mechanics:

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  • Pumps

    • A water pump should circulate the entire volume of water in your system at least every 2 hours

      • Requires 1 psi to raise the water level 2.2 feet

    • Need to keep in mind the head height (distance between the fish tank and the grow bed)

    • Need a pump with at least 100 GPH (however should select a pump with a higher GPH than required because the number is a maximum and can be dialed down)

  • Grow Bed

    • Industry standard is at least 30 cm deep

    • Fish tank volume should be approximately equal to grow bed volume or you can extend it to be a 2:1 ratio

  • Other

    • Stocking Density: 1 pound of fish for every 5-10 gallons of water

    • Ammonia and nitrate levels should be less than 0.75 ppm

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Fish Care:

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  • Fish generally raised with good results: tilapia, bluegill/brim, sunfish, crappie, koi, fancy goldfish, pacu, angelfish, guppies, tetras

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Fish Cycle:

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  • Fish excrete ammonia through both their waste and gills, a substance that can be toxic to fish and plants in large enough quantities

  • Nitrifying bacteria, which live and survive naturally in soils, water and air, convert this ammonia to nitrite and then to nitrate

  • In aquaponics systems, these bacteria will thrive in both the fish tank gravel and in the grow bed medium

  • Plants readily uptake nitrate from the water and consume it, keeping ammonia levels safe for fish and plants to live

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Daily Fish Care:

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  • The only daily input in aquaponics systems is fish food

  • Most fish (including tropical fish) do well on dry flake fish food, being fed in small but frequent quantities

  • The water level in the tank will decrease as water is absorbed by the plants throughout the system, requiring that the tank be refilled every few days

    • Once a month, 10-15% of the water should be siphoned out and replaced with fresh water

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Tank Requirements:

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  • Fish tank can be glass, plexiglass, plastic tub/bucket/barrel, recommended to be anywhere between 3 and 20 gallons, although larger sizes can be used if the space is available

  • Ideally fish tank is in the shade because sunlights fuels algae growth

  • The larger the tank, the larger grow bed area you can support; as a general rule of thumb, 10 gallons of fish tank water can support 1-2 square feet of growing area

  • Planting aquatic plants in a fish tank provide a more natural habitat for the fish and aid in water purification.

Castelo, J. (2018, September 28). Water Pumps for Aquaponics: How to choose the right size for your system. Retrieved from https://worldwaterreserve.com/aquaponics/water-pumps-for-aquaponics/

 

Bernstein, S. & Lennard, W. (n.d.). Aquaponic Gardening Rules of Thumb. Retrieved from https://www.theaquaponicsource.com/rules-of-thumb/

 

https://www.theaquaponicsource.com/blog/aquaponics-how-to-guide-part-2-grow-beds-and-fish-tanks/

Research Update: April 29, 2019

Overview of Plant and Fish Care in Aquaponics: Northern California

 

Aquaponics systems aim to reduce the amount of toxic fertilizer runoff and water waste through a quasi-closed loop biofiltration system. This utilizes nitrogen-rich fish effluent to fertilize plants grown in soilless, floating beds. Nitrifying bacteria pay a key role in aquaponics because they oxidize ammonia or nitrite, which is toxic to the fish in the system, into nitrate which plants uptake (Schaechter, 2009). The clean water then flows back to the fish.

 

Role of Nitrates/Nitrites:

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The balance of of nitrite concentrations is important in aquaponics plant care because too high concentrations can lead to fish death, and too low concentrations will not properly fertilize the plants being grown. It is also important to properly filter the effluent before it cycles through plant beds, for the wellbeing of the plants and fish. Solid waste should be removed from effluent through a preliminary filter (Rakocy, 2012). The extent of filtration depends on the relative concentrations of fish to plants. However, all unstabilized solids must be removed (Rakocy, 2012). One way to do this is through physical filtration. Another way is to expose effluent to high levels of oxygen to encourage aerobic decomposition (Rakocy, 2012).

 

Plant Care:

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Plants require these essential nutrients in high concentration: carbon (C), oxygen (O) and hydrogen (H); and these nutrients in smaller concentrations: nitrogen (N), potassium (K), calcium (Ca), magnesium (Mg), phosphorus (P), sulfur (S), chlorine (Cl), iron (Fe), manganese (Mn), boron (B), zinc (Zn), copper (Cu) and molybdenum (Mo) (Rakocy, 2012). While most of these nutrients are supplied by fish effluent, it is important to periodically test nutrient levels to ensure the health of the system. Many pesticides that are safe for plant use in soil are not safe for aquaponics systems because they can be toxic to the fish in the system. Therefore maintaining an organic system is best. Water temperature and oxygen concentration must also be monitored to ensure healthy plant growth as both effect root respiration (nutrient transformation and uptake). Dissolved Oxygen (DO) levels can be maintained by aerating water throughout the system. Water temperature should be monitored throughout the system, taking into consideration plant and fish species needs. Typically, ideal temperature is around 75℉ (Rakocy, 2012). Temperature can be regulated through heaters, sun exposure, and evaporation cooling. One possible method for heating water in the summer would be floats that allow sunlight through to the water’s surface.

 

Plant Species For Growth in IBCs:

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Generally, the best plants to grow in an aquaponics system are leafy greens, such as chard or watercress, because they have lower nutrient needs. This allows a system to grow more plant mass with less fish and therefore less upkeep. Plants with higher nutrient needs can be grown in aquaponics, but require well-stocked, established systems with higher, well controlled effluent outputs. Fruiting plants are not recommended for small aquaponics systems.

 

Best plants to grow in small aquaponics systems:

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  • any leafy lettuce

  • pak choi

  • kale

  • swiss chard

  • arugula

  • basil

  • mint

  • watercress

  • chives

  • most common house plants

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Best fish to keep in small aquaponics systems:

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  • tilapia

  • blue gill/brim

  • sunfish

  • crappie

  • koi

  • fancy goldfish

  • pacu

  • various ornamental fish such as angelfish, guppies, tetras, swordfish, mollies

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Sacramento Perch as an option for aquaponics:

 

Sacramento Perch are native to Northern California and are a freshwater fish. While they can be found in clear waters, they prefer murky lakes that are clear of plant life. Their diet consists of mainly crustaceans and they tend to dominate the food chain as they are normally the only fish from the Centrarchus genus. Fish under a year old feed mainly on small aquatic crustaceans. As they mature they start to feed on insects such as insect larvae. Adult Sacramento Perch hunt mainly for other fish, including other young perch.

 

Because of their prefered environment and diet, Sacramento Perch are not reccomended for use in aquaponics systems.

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Schaechter, M. (2009). AP [Abstract]. Encyclopedia of Microbiology,Vii.

doi:10.1016/b978-012373944-5.09005-2

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Rakocy, J. E. (2012). Aquaponics-Integrating Fish and Plant Culture. Aquaculture Production

Systems,344-386. doi:10.1002/9781118250105.ch14

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Recommended Plants and Fish in Aquaponics. (n.d.). Retrieved April 28, 2019, from

https://aquaponics.com/recommended-plants-and-fish-in-aquaponics/

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