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Potassium in aquarium

калий в аквариуме

On the potassium in an aquarium is often written, but the controversy about the dosages of potassium from time to time arise. Someone advises to dose potassium additionally with typical fertilizers, someone on the contrary tries to reduce the dose of potassium even in their formulations of fertilizers. In this article, I will explain the reason of such contradictions.

Many beginners after planting of new plants in new aquarium with tap water have first problem – the appearance of small holes on the older leaves of plants, slow plant growth and then problems with algae. All these are signs of potassium deficiency and they occur even in those cases when fertilizer with potassium is used.

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In aquariums with water filtered by reverse osmosis system, on the contrary, dosing of potassium sometimes make plants look worse. Why?

Let us consider three types of aquariums

  1. Aquarium with tap water
  2. Aquarium water filtered by reverse osmosis (RO) mixed with tap water to raise the hardness to the desired level.
  3. Aquarium with pure RO water using GH-boosters such as calcium and magnesium sulphate or chlorides.

With all things being equal (the dosage of fertilizer, the presence or absence of CO2 supply, lighting, number of plants) the required dosage of potassium in these aquariums are significantly different. Why? As you can see, water is the mane difference in these three types of aquariums. To be precise the difference is sodium ions content in these aquariums. Sodium is an antagonist of potassium. It means sodium blocks potassium intake. Therefore, the higher the concentration of sodium in the water, the higher must be the concentration of potassium in it to avoid symptoms of potassium deficiency. Plants do not consume such large amounts of potassium as it can be in water but potassium concentration in water should be higher than sodium concentration. In such conditions potassium can be available to plants.

What about our three types of aquariums in detail?

First type

What is sodium content in these aquariums? Sodium concentration in tap water usually ranges from 5 to 50 mg/L and may be up to 100 mg/L or more but potassium content is usually ten times less. In such planted aquarium potassium content should be at least equal to sodium content or higher. That is why dosing of potassium can be very high. So addition of typical fertilizer with potassium will lead to acceptable concentration of potassium in the aquarium water not soon. Therefore, additional dosing of potassium must be applied. Dose AQUAYER Potassium fertilizer(or AQUAYER AntiChlor+K, which contains the same amount of potassium as AQUAYER Potassium) for such aquariums in first month after aquarium setup. Since the sodium concentration is usually unknown for aquarists the dosing of potassium is very approximate. Aquarist need to be guided by the plants appearance. As soon as signs of potassium lack disappear additional dosing of potassium fertilizers should be stopped. Then optimal potassium content in the aquarium water will be maintained with balanced complex fertilizers AQUAYER Yermolayev`s fertilizer MICRO and MACRO.

калий в аквариуме

Second type

In these aquariums the sodium concentration is 2-3 times lower than in the first type. Why? Tap water is diluted by RO water. But in RO water sodium concentration is close to zero (assuming the use of high-quality membrane). Consequently, the concentration of potassium in this type of aquariums can be 2-3 times lower. Typically, this is achieved only by occasional dosing of AQUAYER Potassium (or AQUAYER AntiChlor+K) after the aquarium setup or when signs of potassium lack appear.

Third type

These planted aquariums do not require additional potassium dosing at all. Because of very low concentration of sodium in RO water. In this type of aquariums plants get enough potassium with the complex AQUAYER Yermolayev`s fertilizer MICRO and MACRO. Even if signs of potassium lack appear aquarist has to be careful the increase of potassium concentration. Because an overdose of potassium can cause shortness of calcium intake and consequently the appearance of signs of calcium deficiency (distorted leafs, whitening of new shoots and further their dying). In tanks of the first type such potassium overdose is unlikely not only because of high concentration of sodium but also because of higher concentration of calcium (higher water hardness) as compared with aquariums of second and third type. In aquariums of third type the risk of blocking calcium consumption due to overdose of potassium is much higher than in the case of the second type aquarium.

What is the conclusion? Potassium, as well as Iron, should be on the shelf of most planted aquarium hobbyists as an addition to the complex fertilizers. Since different types of aquariums and in different time of aquarium the dosing of potassium differs. And, as in the case of iron, some plants absorb potassium with particular enthusiasm, for example, riccia.