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The Effects of Water Temperature in Aquaponics

Water temperature is one of the most critical parameters that an aquaponics grower must maintain consistently. Water temperature affects not only the health of the fish, plants, and bacteria in an aquaponics system. It is also essential for the breakdown and uptake of nutrients and wastes. So, in order to maintain a healthy aquaponics system, the water temperature must be kept in the range that is safe for the fish, plants, and bacteria growing in your aquaponics system. 

There are many factors that can affect water temperature, such as:

  • The capacity and consistency of your source of heat
  • Your climate
  • Ambient air temperature
  • Tank materials
  • Exposed pipings and length of pipes
  • Your growing system,
  • Tanks placements
  • Insulation components of your system
  • The total water volume of your system
  • Available backup systems

These factors will have some effect on your ability to maintain a consistent water temperature. Ideally, we want to minimize our dependence on outside energy sources to minimize maintenance costs and dependency on systems we don't control. Some of the things an aquaponics grower can do to reduce water heating costs are:

  • For those who live in colder climates, insulating tanks grow beds and pipes so that water heat will not easily escape.
  • Some growers bury their tanks in the ground to use the ground as additional insulation and thermal mass. This is fine but, if you decide to bury your tanks, ensure that you properly insulate underneath and around the tanks to decouple them from the ground. 
  • Insulate and seal leaks in your greenhouse or whatever structure you are growing to maintain a consistent air temperature.
  • Using environmental control systems like water or air heaters is also essential in managing and maintaining a consistent air and water temperature.
Aquaponics Water Heater

The Optimum Temperature Range for Aquaponics

Overall, a general compromise water temperature range is 68-86 °F or 20-30 °C. Here are the water temperature ranges of the fish, plants, and bacteria in an aquaponics system.

Fish:

  • Tropical Fish: 71-89 °F (22-32°C)
  •   Cold-Water Fish: 50-64°F (10-18°C)

Plants:

  • Most vegetables: 64-86°F (18-30°C)
  • Some vegetables like lettuce and cucumber: 46-68°F (8-20°C)
  • Other vegetables Like basil: 62-86°F (17-30°C)
  • Leafy Greens: 78°F (26°C)

Bacteria:

  • Grows in 62-93°F (17-34°C)                    

    Plants

    Plants are affected by the water temperature more than the air temperature in an aquaponics system. Your ability to control the water temperature will depend on where you are growing your plants (outside or indoors). It is more challenging to maintain your water temperature if you are growing outside than on the inside. It is also important to consider the important factors like plant’s suitability to your climate when choosing plants to grow in your aquaponics system.

    Effects of High Water Temperature on Aquaponics Plants

    Too high water temperature will lead to heat stress in your aquaponics plants. The plants will shut their roots and go into survival mode when the water temperature is too high. It is also important to note that the severity of heat stress that the plants suffer is affected by the air temperature and humidity.

    Symptom of Heat Stress to Plants:
    • Wilting
    • Low levels of DO (dissolved oxygen)
    • Plants will start to drop the flowers and stop fruiting
    • Roots get slimy
    • Soft brown spots on fruits
    • Roots turn black and die

    Effects of Cold Water Temperature on Aquaponics Plants 

    If you live in colder climates, problems can arise during winter, fall, or early spring if your aquaponics system is located outside. Cold temperatures can stunt a plant's growth. You will begin to observe a reduced growth on your aquaponics plants when the water temperature drops below 60 °F (15 °C). 

    Fish

    Fish are poikilothermic or cold-blooded animals, meaning they cannot regulate their body temperatures like humans or other animals. They just rely on their external environment to regulate their body temperature, and it is also essential to understand that fish live within certain temperatures. Unlike plants, fish can't deal with significant water temperature changes. The high and low temperatures will have an effect on the fish and the entire system. 

    Fish can be categorized into cold water, cool water, and warm water fish. Warm water fish like catfish, carp, and tilapia thrive in high water temperatures of 71-89 °F (22-32°C). But cold-water fish such as trout prefer a colder temperature of 50 - 64°F (10-18 °C) to thrive. While some cool water or temperate water fish such as largemouth bass and common carp have wider ranges and can tolerate temperature range of 41 - 86°F (5-30°C). In choosing the best fish for your aquaponics system, there are several factors that you will need to consider; check this guide to the best fish in aquaponics

    A stable temperature will not only keep your fish happy, it will also:

    • Keeps fish healthy
    • Aids faster fish growth
    • Minimize fish stress and diseases
    • Helps in the efficient feed conversion

    The rise in water temperature helps with the metabolism, rate of respiration, and oxygen requirements of the fish. Fish appetite for tropical fish such as tilapia are also affected by the water temperature. So take note to reduce the feeding during colder months or winter season. To avoid problems with your aquaponics fish, grow fish that adapt to your local environmental conditions. 

    Aquaponics Fish Tank

    Bacteria

    Water temperature is essential for bacterial growth. The optimal water temperature range for healthy bacterial growth and productivity in an aquaponics systemis 62-93°F (17-34°C). The bacterial growth rate will decrease when the temperature is below 64°F (18°C) and will die when the temperature is lower than 32°F (0°C)

    Conclusion

    The water temperature range for aquaponics is 68°- 86°F (20-30°C). The bacteria, plants and fish thrive in this range. It is essential to choose a combination of fish species and plants that are suitable for your location and environmental conditions to avoid problems and lower your maintenance costs.

    Always remember that if your water temperature is too high, it will diminish the solubility of the dissolved oxygen, which will cause fish stress. When the water temperature is too low, the bacteria will stop working, and plants' growth will slow down. Thank you for reading our article. Pleasesubscribe to our mailing list to get aquaponics updates.

    Before we close this article, here are our recommendations on how you can avoid water temperature problems in your aquaponics system.

    • Plant your aquaponics system accordingly; if you want to grow outdoors, ensure that your system is not exposed to cold if you live in colder climates or too much sun exposure if you live in warmer climates.
    • Carefully choose the right choice of plants and fish to meet their optimal water temperature ranges.
    • Choose plants and fish that are suitable for your local climate to avoid water temperature problems. However, there are some techniques that can be used to minimize water temperature fluctuations and extend your growing season.
    • Shield your fish tank from the sun or protect your tank from cold using insulations or water heaters. You can use a solar panel to lower your electrical cost. 

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