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Everything You Need To Know About pH Aquaponics Troubleshooting

Aquaponics pH Troubleshooting Guide

The importance of pH levels in an aquaponics system; what it is, what it affects, and how to monitor, raise and lower pH levels in your setup…

As any grower will tell you, pH levels are a direct indicator of the system’s health, and maintaining correct levels is, in fact, so important that any deviation too far outside optimal ranges will  have drastic consequences if not rectified in a swift manner.

Playing such a major role it’s not surprising that pH is often touted as the most important level to monitor when doing aquaponics, and that’s not wrong, in fact you could say that it’s twice, if not thrice, as important since both the plants and fish, as well as the bacteria, are all living components of the system that are affected by changes in pH levels.

The Importance of pH in Aquaponics

Although maintaining optimal pH levels for plants and fish may sound straightforward, and in most cases it typically is, there is a slightly finer line to tread when running aquaponics systems since it combines three living organisms that each require different pH levels to survive, yet they are all contained within the same closed-loop system and all share the same source of water.

In this case, we’re essentially trying to replicate the processes that happen in nature, therefore aquaponics systems generally require a compromise that sets a safe range for all three inhabitants; somewhere between 6.8-7.2.

Maintaining an optimal pH level will aid the nitrogen cycle/nitrification process; the most important process keeping the system alive and producing those satisfying harvests with plentiful yields; no matter what plants and fish you choose. 

Factors That Can Affect pH in Aquaponics

pH levels affect every aspect of the system, from feeding and growth, to nutrient conversion, availability and uptake, as well as filtration and cleansing. There are a number of different factors that can affect the pH levels in an aquaponics setup, and these include:

Biological Processes: The biological processes that happen inside an aquaponics system can all have an affect on pH level. The relationship between these processes will cause levels to naturally fluctuate, which is why it’s important to constantly monitor and be acutely mindful of your safe operating range/s.

Release and Breakdown of Fish Waste: Waste excreted by the fish releases ammonia into the water, which in turn makes the solution more alkaline and increases pH levels.

The Nitrification Process: Conversely, the nitrification process that converts the ammonia fish waste into nitrites, and then into nitrates that the plants can consume, will increase acidity of the ecosystem and therefore lower pH levels. This is a natural process that, once the system has been cycled successfully, will balance itself out. But after the fish and plants are in place, waiting is no longer a viable option, instead you’ll need to employ one or more techniques to raise or lower levels pH manually.

Fish Health: Like all components of the system, fish are sensitive to changes in pH levels, and do not react well if levels fall outside ideal ranges. High pH levels can increase the toxic ammonia, which is harmful to the fish, whereas low pH can cause the levels of dissolved carbon dioxide to rise, which can lead to respiratory problems.

Plant Uptake and Respiration: As plants take on nutrients and photosynthesize they absorb carbon dioxide, which increases pH levels. Then during the night when the plants respire, carbon dioxide is released and pH levels will decrease. Again, this is why it’s highly important to take regular, accurate readings so you can always keep levels within safe operating ranges.

Water Quality: Depending on your location, the water source pH may be naturally high or low. Prior testing followed by any necessary adjustments can help better maintain healthy and stable pH levels in your aquaponics system.

General Hardness: Harder water, which has more dissolved levels of minerals, is more alkaline and will present pH levels around 8.5, whereas soft water is more acidic, has much lower levels of dissolved minerals and is closer to neutral pH.

Dissolved Oxygen DO: It’s also important to monitor dissolved oxygen levels as it is critical for the nitrifying bacteria to convert the nitrogen contained within the ammonia waste. Some experts don’t consider this process to be directly related to pH, however some studies suggest that the presence of pollutants and contaminates does indeed affect the level of oxygen in the water, thus inhibiting the lifespan of algae and therefore increasing the pH level. Whilst the consensus on this might still be out, it’s agreed that DO does affect the nitrifying bacteria’s ability to perform its conversion, therefore remains an vital part of the balancing act that is stabilizing your aquaponics set up.

The recommended level of DO is around 5 ppm, or slightly higher; warm water fish can not survive when levels drop lower than 3ppm, and cold water fish require minimum level of 4 ppm.

    • DO levels can drop on cloudy/rainy days since there is less sunlight to for the plants to photosynthesize and produce oxygen.
    • Too many fish in the tank, as well as too much uneaten food, can also reduce levels.
    • And water that is too saline, will also see a reduction in DO levels.
Aquaponics pH Troubleshooting Guide 1

Optimal Levels Aquaponics

Whilst it’s common practice to use chemicals in to adjust pH levels in a hydroponics setup, it’s also possible to do so naturally in an aquaponics system.That said, this natural process takes time, so in cases where time is of the essence, you can turn to the chemical method to get levels stabilized in your ecosystem much faster.

Importance of Cycling Aquaponics System First

Since aquaponics leverages all natural processes, it’s extremely important to let the whole ecosystem perform one full cycle before plants are grown. Each process needs time to establish itself, be it a few days or several weeks. For example, the fish need a short amount of time to acclimate, eat and excrete the ammonia waste that provides the stage of the fuel for the process.

The nitrifying bacteria, which colonizes on the sides and surfaces of the tanks/pipes, grow bed media and on the biofilters, can take anywhere from 4-8 weeks to mature. This step is the most critical given that insufficient growth of bacteria will cause too little nitrogen to be converted and thus, the plants will be unable to survive.

Note: Although there may be related indicators that can reveal certain health problems with the system, most of the consistent symptoms only become apparent when it’s very nearly too late. For that reason it is crucial to follow the guidelines and not rush the process, even by a day or two.

Approx. Overview of Optimal levels in Aquaponics

  • pH levels – 6.8 to 7.2 pH
  • Alkalinity – between 50 and 300 ppm
  • Ammonia concentration – between 0.29 and 0.49 mg/L
  • Nitrite concentration – Toxic to most fish at 5ppm, suggested level of 1ppm or less
  • Nitrate concentration – Safe for fish between 50-90 ppm, suggest level of 60-70 ppm for plants nutrient uptake, without being toxic to fish.
  • Electro conductivity – from 661.0 to 682.3 μS/cm

Raising pH in Aquaponics

Overfeeding is one of the most common causes behind rising pH levels. As the fish produce more excrement, more ammonia is released into the water, in turn raising the pH levels.

To prevent or counter pH level rising, you can:

  • Remove uneaten food
  • Remove excess waste
  • Remove some of the fish
  • Changing the water will also help lower acidity levels to bring the system back to a more neutral pH

In addition:

  • Adding calcium carbonate and potassium carbonate in equal amounts will also help raise pH levels.


Lowering pH In Aquaponics

On the other hand should your system be too alkaline, and you wish to lower the pH level, you can:

  • Add nitric, muriatic, potassium hydroxide or phosphoric acids bit by bit to lower pH levels
  • Use a grow bed media that’s slightly alkaline, such as crushed lava rocks or limestone
  • Changing the water can also help lower alkaline levels to bring the system back to a more neutral pH

In addition:

  • Installing a Reverse Osmosis RO filter in your system can also help lower pH levels. Placed before the incoming water supply and RO filter can remove additional contaminates before it enters the system.
6 in 1 test strip

How To Monitor Levels Aquaponics

There are three main ways to monitor pH levels in your aquaponics systems. These include:

Test Kits/Water Test Kits: simple, cost effective

There are many test kits on the market, most are capable of measuring a handful of factors. For example the popular Tetra Test 6 in 1 test strip can provide most of readings required to balance an aquaponics system. This includes:

  • Nitrate
  • Nitrite
  • Hardness
  • Total chlorine
  • Alkalinity
  • pH

When it comes to testing the water, the Tetra test is able to measure general hardness and pH, however, if you’re looking for accurate readings of dissolved oxygen, then the Tetra Test O2 is your best bet.

pH Meters: expensive but extremely user friendly and accurate

These devices measure hydrogen ion activity to determine the acidity/alkalinity of a solution. 

pH meters are high accurate and eliminate human error such as misreading due to colorblindness. They are a lot more expensive than test strips but provide much more precise results.

Continuous Monitoring Systems: expensive, accurate, uses sensors to provide consistent readings

These systems, also known as Smart Automation Aquaponics Monitoring Systems, are relatively new; first being mentioned in the research papers of Muhammad Saef Tarqani Abdullah, in 2022. They aim to provide continuous reading for the most accurate and efficient aquaponics setups. Since the technology will, no doubt, inflate initial setup costs these systems hope to advance the commercial side of the industry.

Remember, as the ecosystem adjusts and balances itself, the levels of ammonia, nitrogen, and the pH will change. That’s why it’s essential to allow the system to cycle fully before beginning to grow plants and hone your technique.

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Further Control For Changes in pH

Regardless how precise your setup is, sometimes the water source may present you with unexpected swings in pH levels. This, as you may have guessed, is a bad thing since most fish cannot handle the rapid changes, beneficial bacteria can die off completely, and you’ll be forever monitoring levels paranoid any slight change could be the start of something a lot more drastic.

Fortunately there’s a simple, effective way of managing this; by creating a buffer – a weak acidic substance dissolved in water to help prevent rapid changes in pH.

To create this buffer you will need to test for carbonate hardness (KH) and general hardness (GH). A buffer is present when readings of 4 dKH (degrees of KH) are shown, and the larger this number, the more of a buffer the system has.

To adjust these levels you can add potassium bicarbonate at a ratio of 2.5tsp: 100 gals of system water for each dKH level that you need to increase. With this buffer in place, any changes in pH level will be slowed; giving you more time to spot and rectify the issue. 

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