Aquaponics water values ​​– what to measure and why?

Questions often arise about water measurements in aquaponics systems. What pH value is optimal? How do I know if there is enough oxygen in the water, what NH4 value is OK, and why do we measure ammonium, nitrite and nitrate again?

In any case, an aquaponics system should have a stable balance and regulate itself as an independent ecosystem. This is basically true. However, if problems arise, which in most cases are due to errors in the system design or operation, water values ​​can quickly provide information about the cause. This allows you to react quickly to problems. With routine measurements and a good eye for an aquaponics system, you can of course also prevent problems wonderfully.

PH value

The pH value is a measure of the acidic or basic character of the water. The value 7 describes the neutral range. Below 7 is the acidic range, above 7 is the alkaline range.

Why measure the pH value?

Bacteria and microorganisms can only live in a certain range, which can vary from species to species. While trout tolerate a range between 5.5 and 9.2, carp, for example, are even more frugal with values ​​between 5.0 and 10.8. However, we are talking about extreme limits here that should not be understood as a permanent condition anyway.

What range should the pH value be in aquaponics?

Due to the different types of fish and plants, a pH range between 6.0 and 8.0 should be aimed for in aquaponics. It is also interesting that the pH value also provides information about ammonium (NH4) and ammonia (NH3). If the pH value is above 7, i.e. basic, then we are talking about ammonia (NH3). If the value is below this, i.e. in the acidic range, we are talking about ammonium (NH4) - the conjugated acid of ammonia.

You should also know that the accumulation of ammonia (NH3) is more dangerous for fish than that of ammonium (NH4). So if the pH value is below 7, you don't need to worry about ammonia, which is so toxic to fish.

Make absolutely sure that the components of your aquaponics system do not affect the pH value. This starts with the grow bed and fish tank . Be sure to use plastics that are free of plasticizers and heavy metals. Food-safe PVC-U pipes have proven to be effective. Also use pH-neutral grow media .

Ammonium (NH4) & Ammonia (NH3)

The metabolism of the fish puts a strain on the purity of the water. This happens primarily through the release of ammonium via the fish excrement. The fish eat the fish food and then excrete it again. This creates the chemical compound ammonium (NH4), which damages the water quality and thus the fish in the long term. Depending on the pH value, the compound ammonia (NH3), which is toxic to the fish, can also increasingly form if no well-coordinated biology counteracts this.

But ammonium is not only released through feed and fish excrement. Large amounts of ammonium are also released when biomass, such as dead plants or dead fish, decomposes bacterially.

The release of NH4 starts the nitrogen cycle , the most important process on which the concept of aquaponics is based. Ammonium is the first basic requirement for the cycle to get going. The plants only get their nutrients through the breakdown of organic substances via the step proteins > ammonium > nitrite > nitrate.

Why measure ammonium?

By determining the ammonium value, you can see relatively easily whether the "biological engine" of your system is getting "fuel". Especially at the start, in the so-called "cycling phase", you can see whether your fish are already producing ammonium or ammonia.

Ask yourself:

• Is your system stocked with enough fish?
• Do you feed your fish often enough?

If, however, you measure very high ammonium values ​​( >0.5 ppm ), this means that your biofilter or your grow beds are probably not working properly or are unable to cope with the amount of ammonium produced (e.g. due to under-dimensioning of the filter medium and insufficient colonization by bacteria and microorganisms ).

Ask yourself:

• Is your grow bed and your biofilter large enough to provide enough space for bacteria and microorganisms to thrive?
• Do you have too many fish in relation to the filter capacity in your system? Are you feeding too intensively?
• Are there possibly dead fish in the tank?

What range should the ammonium NH4 value be in aquaponics?

NH4 is measured in mg/l or ppm (parts per million). The color scale of our ammonium (NH4) test kits ranges from <0.05 to 5 ppm . In principle, the aim should be to achieve a value as low as possible.

Nitrite (NO2)

Nitrite is an intermediate product in the nitrogen cycle and is more of a means to an end. Nitrite bacteria, nitritifiers - so-called Nitrosomonas are responsible for converting the previously enriched ammonium into the intermediate product nitrite. Nitrate is then formed from nitrite through oxidation and Nitrobacter bacteria . Nitrate is the nitrogen compound that is responsible for plant growth.

Why measure nitrite (NO2)?

As an intermediate product, nitrite provides information about the process of nitrification, the process of providing nutrients for plants and breaking down toxins.

If the value is too high ( >0.5 ppm ), this indicates a problem or blockage in nitrification. This means that your Nitrobacter and Nitrosomonas bacteria are either not working enough or are not working effectively enough.

Again, check the dimensions (volume) of your grow beds or biofilter in relation to the fish tank, fish stock and feeding cycles.

Bacteria and microorganisms work less effectively at low temperatures and virtually stop working below 5°C.

Ask yourself:

• Are there other, unintended ammonium producers such as dead fish, rot or similar in the system that the bacteria from your biofilter may be inferior to?

The nitrite value gives you information about the stages of nitrification and shows you whether your water may even be toxic to fish.

What range should the nitrite NO2 value be in aquaponics?

NO2 is also measured in mg/l or ppm (parts per million). The color scale of our nitrite (NO2) test kits ranges from <0.01 ppm to 1.0 ppm .

If the nitrite (NO2) value exceeds 0.5 ppm , this is a sign of a blockage or overload in the nitrification process. If the value is in the yellow color scale, you can assume that the provision of nitrate = nutrients for your plants and the breakdown of toxic ammonia and nitrite is working well.

Nitrate (NO3)

If the nitrification described at the beginning, the breakdown of ammonium via nitrite to nitrate, works, the plants finally get what they need – their nutrients.