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Phosphates (PO4) in the Aquarium! Friends or Enemies? Be the first to know!

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We continue to study aquarium chemistry. And today we will quickly deal with one more representatives of her in the aquarium. And their name is and phosphates (PO4). They are not as scary and dangerous as ammonia or nitrites, especially for fish. But the increased content of phosphates in the aquarium, almost always lead to a sharp increase in algae. And that's why.

phosphates Are stable chemical compounds of phosphorus. And phosphorus is very useful for all living organisms. It participates in cellular exchange and serves as a source of energy. phosphates, like nitrates, are very actively absorbed by living plants in the aquarium. It would seem, what's the problem, if they are useful? And the problem is that they are loved not only by plants, but also by algae. And if of phosphates it becomes much, the plants cease to cope with them and the algae are taken for their work. Water and walls become green, the level of oxygen falls, and this indirectly affects the health of the fish. And as we know, with algae it is sometimes very hard to fight. Therefore, it is better to keep norms of phosphates within acceptable limits close to zero.

Phosphate test for aquarium can be seen in this image. Phosphates The test for the aquarium can be seen in this picture.
Phosphates (PO4) / Test suite.

Sources of of phosphates in the aquarium.

Sources of of phosphates in the aquarium serve:

  • Decaying plant residues.
  • Fish feces.
  • Dead algae.
  • Dead fish.
  • Fish slime.
  • Conditioners for stabilization of water parameters.
  • Tap water can already contain and phosphates.

But the biggest source of phosphate is dry food. Imagine, only 5 grams of dry flakes are able to raise the level of phosphates on 0,4 mg / l .. And this despite the fact that the ideal level of phosphates in the aquarium is the indicator 0,5 mg / l. When the level is raised to 1 mg / l. already begin to grow algae. Especially in aquariums without living plants.

Feed manufacturers specifically add and phosphates in the food for its conservation. And if you have problems with phosphates in the aquarium, read the composition of the feed, and choose the feed with the smallest content in it.

Measuring and lowering the level of phosphates in the aquarium.

Phosphate test in my aquarium can be seen in this picture. The phosphate test is shown in this image.
Phosphates (PO4) Test.

For determining of phosphates In the aquarium, I usually use drip tests. The procedure is quite simple. Mix the special solution with aquarium water and compare the color with the table from the kit.

But there are a couple of moments. First, as mentioned above, tap water may already contain some amount of phosphates. Secondly, tests show only inorganic and phosphates, dissolved in water. But they will not show availability of phosphates, settled in the ground and of phosphates organic origin. And if you do not have any phosphates in the aquarium, it does not mean that they are not there at all.

✅ Advice. Always check the production date and expiration date of any tests for the aquarium. After all, for example, in solid laboratories the composition of the test is prepared on the day of measurement, and the next day it is not trusted! Therefore, the expiration date is very important for the accuracy of measurements.
Ways of struggle.

The fastest and most effective way to reduce of phosphates, is a partial change of water in the aquarium. But only in the absence of them in fresh water.

As and phosphates are able to precipitate, then to reduce them, it is also necessary to siphonize the soil, clean the glass and decor elements.

Plus, now on the market for aquarium products, there are a lot of products for lowering of phosphates in water. These funds not only lower and phosphates, but also prevent the growth of algae.

Here are links to some of them:

Tetra PhosphateMinus
Sera phosvec clear
When it is necessary to increase the phosphate in the aquarium.
Algae nitrate phosphate Redfield ratio can be seen in this picture. The ratio of nitrates to phosphates and the appearance of algae in the aquarium are shown in this image.
The Ratio of Nitrates-Phosphates and Algae Growth!

phosphates in the aquarium, although not as dangerous as ammonia or nitrites, but in order to avoid problems with algae, it is better to keep them at the lowest possible level. Exceptions are aquariums with a large number of plants and a small number of fish. The so-called planted aquariums. For them of phosphates may not be enough and you have to add them additionally with the help of special means and fertilizers. Such as, Sеechem Flourish Phosphorus, eg. But with them you need to be very careful, read the instructions and monitor the level of phosphates after use. And also to monitor the ratio of phosphates and nitrates. But such solutions are more suitable for professionals.


If you want to delve into the topic with algae, you can try to adjust the balance according to the Redfield table. We do tests for phosphates and nitrates, and then we look at what are your chances for the appearance of algae in the aquarium. But do not forget that the right balance, plant growth and getting rid of algae, also requires trace elements, potassium, iron and a properly selected lighting aquarium!

Related articles:

Ammonia in aquarium! Danger!

Nitrite in aquarium! Danger!

Nitrates in aquarium!

Phosphate test. Test for phosphates in the aquarium.
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Phosphate test. Test for phosphates in the aquarium.
Phosphate at the aquarium. Only personal experience! Phosphates in the aquarium! How to conduct tests, as well as raise or lower phosphates in an aquarium. Personal experience!
Vadims Krjuckovs
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