▷ Nitrate – NO3 in the aquarium | cause, and regulation

Connection between water quality and nitrate value

The absolute level of the nitrate value does not give any direct indication of the water quality. The nitrate value can already be high in tap water.

The absolute level is at best an indirect indicator, since other pollutants are often also present in high concentrations when nitrate levels are high.

More important is the increase in the nitrate value between two water changes and the comparison with the nitrate value in tap water.
Nitrate is released by bacteria from organic components, the proteins.

A rising nitrate value is therefore an indicator of higher organic pollution of the water.

How high nitrate levels arise

Nitrate (NO3) is formed in nitrogen cycle out of Feed residues, plant residues, urine and faeces. If the nitrate level is constantly too high, it is reasonable to assume that fed too much becomes. Either the amount of food per fish is too high or there are too many fish in the aquarium and the total amount of food is too high.

Normally it is enough, the fish once a day to feed. Only as much food is given as is eaten within approx. 5 minutes. It there must be no food left. One day a week will not fed at all.

The filter size must be appropriate for the aquarium size. It is better if the filter is one size too big. The filter material is only cleaned when only a little water flows through it. During cleaning, the filter material is only rinsed out with warm water, not thoroughly cleaned. The view that the cleaner the filter, the cleaner the aquarium water is, is wrong.

If the fish stock is too high, the stock must either be reduced, a larger aquarium used, or the nitrate produced must be removed by more frequent and larger water changes. It can also help if the sludge is vacuumed off regularly. If they are fed moderately, it is usually not necessary to vacuum up the sludge.

Fast-growing plants consume a relatively large amount of nitrate as a nutrient and can thus slow down an increase in nitrate levels. The roots of some houseplants, e.g. B. Efeutute or Philodendron, can be hung in the aquarium water. These plants also consume a lot of nitrate. The nitrate value then often drops to zero. A rapid increase in the nitrate value within a few days cannot be prevented in this way.

Alternatives for determining water quality

Better standards for water quality are DOC (Dissolved Organic Carbon), TOC (Total Organic Concentration), BOD5 or the saprobic system. However, the corresponding tests can only be carried out in a laboratory. Measuring the nitrate value is therefore the only method suitable for aquaristics.

Nitrate value = 0, can that be right?

A nitrate value of zero can definitely occur in the aquarium.

The prerequisite is that at least as much nitrate is consumed by the plants as is newly produced through the nitrogen cycle.

Some aquariums even have to be supplied with extra nitrate so that the plants have nitrate available.

Conditions for a nitrate value of zero

Possibly these measures are supported by not eating live food and moderate feeding with catfish tablets and lots of plant food, such as lettuce, peas, etc.

With the help of a few houseplants whose roots hang in the aquarium, the nitrate level can be reduced to zero, even if the other conditions are not ideal. Suitable are e.g. E.g. ivy, monstera and willow branches.

nitrate and phosphate

How much nitrate and phosphate should there be in the aquarium water?

There are two different views on the subject of nitrate and phosphate levels in aquarium water.

The aquarium water should contain as little or no nitrate and phosphate as possible.

The aquarium water should have a nitrate content of 10 mg/l and a phosphate content of 0.1 to 0.2 mg/l.

Experiences

While some aquarists have found that appreciable levels of nitrate or phosphate lead to plagues of algae, other aquarists experienced deficiency symptoms in the plants when too little nitrate or phosphate was detectable in the water. According to this, aquariums with a small stock of fish and a lot and strong plant growth can apparently suffer from deficiency symptoms. Sometimes increased plant growth is observed just before the water change. In such aquaria, reducing water changes can result in higher nitrate and phosphate levels. The result can be a growth spurt in the plants.

In aquariums with normal or high fish stocks and relatively few plants, detectable levels of nitrate or phosphate easily lead to excessive algae growth.

arguments

Nitrate should be detectable at 10 mg/l and phosphate at 0.1 to 0.2 mg/l

Ideally, exactly as much nitrate and phosphate is produced as is needed and consumed at the same time. It is therefore important to aim for the lowest possible nitrate and phosphate content. Nitrate and phosphate that is not required is removed by changing the water or nitrate filter, because otherwise there is a risk that too many algae will grow.

The constant supply of nitrate and phosphate is more important than the absolute level of the nitrate and phosphate value. If the supply is evenly distributed, the absolute level of the value can be low. If supplies can falter, gaps in supply must be compensated for with a higher value. Since plants store a lot of nutrients, short-term gaps can be bridged even without high nutrient levels in the water. Plants store different nutrients differently. Therefore, potassium is more of a limiting factor than nitrate or phosphate.

In aquariums with many plants, few fish and strong lighting, adding nitrate and phosphate can make sense if more nitrate and phosphate is needed than is produced.

Advantages and disadvantages of nitrate resins

Nitrate filter as an alternative

Biological nitrate filters can be more useful than nitrate resins. In addition, a diaphragm pump and a redox measurement are useful. If the redox value falls below -250 mV, air is supplied with the membrane pump. Otherwise, hydrogen sulphide and the corresponding smell of rotten eggs can develop.
The bacteria in the filter breathe nitrite and nitrate. In doing so, they give off nitrogen. At the redox value -260 mV, all nitrite and nitrate has been breathed out. The bacteria then breathe sulfate SO4— and give off hydrogen sulfide H2S.

Depletion of nitrate in the aquarium

How is nitrate broken down in the aquarium:

The sap of fast-growing plants can contain hundreds of times the amount of nitrate in the surrounding water. The plants form nitrogenous storage substances. By trimming the plants, the nitrogen is removed from the aquarium. In aquariums with permanently fast-growing plants, nitrate is usually not a problem.

Some types of bacteria also absorb nitrate and also form nitrogenous storage substances from it. When removing mulm and filter sludge, the nitrogen is removed from the aquarium.

Filter resins work according to the exchange principle. They must be regenerated regularly with table salt. In addition to nitrate, filter resins also bind other substances that are useful. They also salt the water. Filter resins can therefore do more harm than good.

Certain types of bacteria can breathe nitrate instead of oxygen. Normally, these bacteria prefer oxygen for respiration. If little or no oxygen is available, the bacteria breathe nitrate. So, nitrate respiration is not the uptake of nitrate as a nutrient. Nitrate is used for energy production (respiration).
In addition to the nitrate, there must be a substance that can be inhaled. This can e.g. B. dissolved carbon compounds in the water.

In a nitrate filter, bacteria break down nitrate into nitrogen and nitrous oxide. Because they regularly need carbon, the bacteria in nitrate filters are fed fish excrement, vinegar, PVC plasticizers, methanol, vodka, lactose or paraffin. The bacteria are not picky and will take almost anything.

Nitrate filters are often self-made and are then not harmless. If used improperly, fish can be killed. A safe and similar method is the biotrope stabilizer from Dennerle.

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