Fish raised in aquaponics systems require good quality water to grow healthy. This means that water parameters such as dissolved oxygen, carbon dioxide, ammonia, nitrite, nitrate and pH must be within the ideal acceptable parameters. In this article, we will discuss the ideal water parameters in aquaponics and how to measure and fix water quality issues in your aquaponic system.
Water is the lifeblood of an aquaponic system. It is the medium in which all the essential nutrients are transported to the plants and a medium that the fish received oxygen. All parameters are important and impact the three main elements of an aquaponic system: fish, plants and bacteria.
The main goal is to maintain a healthy recirculating ecosystem with water quality parameters that provide enough nutrient requirements for the growing fish, plants, and bacteria.
Water temperature influences not only what type of fish you can raise and what plants you can grow and the performance of your bio-filter. Fish are temperature dependent, goldfish, bass, catfish and tilapia are warm water species that prefer temperatures ranging from 65 to 85°F. Cold water species such as trout thrive at a temperature ranging from 55 to 65°F range. Vegetables grow best at a temperature ranging from 70 to 75°F while bio-filters (nitrifying bacteria) perform best at a temperature ranging from 77 to 86°F. Prolonged water temperature outside of your system’s acceptable range can cause harm to the fish, plants, and bacteria. (1)
The pH of the water has a major impact on fish, plants and bacteria. pH control plants access to essential nutrients. The ideal pH range for aquaponics is between 6-7; outside this range, the nutrients become difficult for the plants to access. (1)
Ammonia is released when organic matter decays. Ammonia is excreted by the fish through its gills and through urine. Ammonia is toxic to the fish. A higher level of ammonia can kill the fish and a low level of ammonia can be stressful to the fish.
Like ammonia, nitrite is also toxic to the fish. High level of nitrite can lead to rapid fish deaths and low levels of nitrite over an extended period can result to fish stress, diseases and death. (1)
Nitrate is far less toxic to the fish compared to ammonia and nitrite. While nitrate is a nutrient produced by bio-filtration, too high level of nitrate (over 150 ppm) is a sign that not enough plants are grown in the grow bed to absorb all the nitrates in the water. (1)
Dissolved oxygen is a very important parameter for growing fish and also important to the nitrifying bacteria that convert fish waste into nutrients for the plants. Warm-water fish requires about 5 ppm of DO and cold-water dish requires about 6.5 ppm of DO to maintain fish health and growth. Oxygen level should be measured frequently in a new system, but once your system is established, you need not measure your water DO often. (1)
Other Components of Water Quality:
Algae are photosynthetic organisms similar to plants that readily grow in any body of nutrient rich water that is exposed to sunlight. The presence of algae in an aquaponic system can affect the water quality parameters of pH, DO and nitrogen levels. (4)
In aquaponics, it is important to prevent algae from growing because they can give problems to the system. They will consume the nutrients in the water and can reduce the DO levels in the water at night that can cause fish death. Lastly, algae can clog drains and block filters in the system that can lead to water circulation problem. (4)
Parasites and other bacteria and small organisms living in the water
Over time, other organisms such as will be present and contribute to the system. Some of these will be helpful such as earthworms while others are threats such as parasites, pests and bacteria that are impossible to completely avoid. To prevent these threats from becoming dangerous infestations is to grow healthy plants and fish and by ensuring a highly aerobic condition in your system, with access to all essential nutrients. In this way, these organisms can keep away infection or disease using their own healthy immune systems. (4)
Low dissolved oxygen
Lethargy and piping (fish swimming close to the surface)
Insufficient water flow or aeration.
Overcrowding of the fish.
Move some fish to other fish tanks.
3Add more air and water flow.
Gas supersaturation (gas bubble disease)
Gas bubbles in eyes and gills.
Cranial swelling and popped eyes
Pipes on the suction end of the pumps are sucking air into the pipeline.
Excess addition of oxygen.
Aerate water to vent pressurised gas.
Check and repair any sources of air intrusion to the system.
(hypothermia and hyperthermia)
Hypothermia: Fish become inactive and depressed.
Hyperthermia: Fish stop feeding.
Water heater or chiller failure.
Undersized heaters of chillers
Use the right size of water cooling or heating for your aquaponic system.
Cover the fish tank and apply insulation to tanks and pipes.
Pale or brown gills.
Brown blood, dyspnoea (fish cannot breathe even with adequate oxygen levels)
Solids or fish feed accumulation in the system.
Stop feeding and remove excess feeds.
Change the water.
Find the cause of biofilter failure. Adding 2-6 gr of salt per litre of water reduces toxicity.
Fish are hyper-excited - bolting and jumping.
Fish stopped feeding.
Biofilter failure, undersized biofilter or too much feeding.
Stop feeding and perform water exchanges. Find the root cause of a biofilter failure.
Growth retardation, poor feed conversion and erratic swimming behaviours
Nitrate accumulation occurs naturally in systems with high recycling rates.
Increase water exchange rates in the system or add more plants.
pH does not affect the fish directly, but it influences other water quality parameters. Check for clinical signs for ammonia toxicity and excess CO2 when pH swings
loss of system pH buffering capacity. Accidental addition of pH modifiers. Excessive degassing of water (pH rises) or loss of system degassing capacity (pH lowers)
Restore alkalinity to at least 100 mg/l (of CaCO3). Gradually adjust pH to normal levels. Adjust the degasser’s air flow.
To maintain good water quality in your aquaponic system, it is recommended to perform water tests once in a week to make sure all water parameters are within the ideal level. However, established and mature aquaponic system need not be tested often as they will have a consistent water chemistry, so testing is only needed when there is a suspected problem. Daily fish health and plant monitoring are also helpful in the early detection of problems.
In water testing, colour-coded freshwater kits are easily available. These kits are easy to use and include tests for ammonia, nitrite, nitrate, GH and KH. test can be done by adding 5-10 drops of a reagent into 5 milliliters of aquaponic water. Each test takes about five minutes to complete. Other methods of water testing include digital pH, nitrate meters, or water test strips. (4)
pH, nitrate and water temperature are the most important weekly tests because the result shows the balance of the system. It is recommended to record your test results so changes can be monitored easily. (4)
Keeping your aquaponic water within the ideal water parameters is important for the health and success of your aquaponic system. Monitoring your water quality parameters such as pH, DO, temperature, Ammonia, Nitrites and Nitrates on a regularly can help to avoid problems in your aquaponic system. Thank you for reading, join our Facebook group for more information about aquaponics.