Phosphate tests (PO4-test): which is more convenient?

Phosphates in the aquarium are evil. Why? Explanations in special materials on Akvariumka: Why phosphates in the aquarium harmful? ;"High" nitrates and phosphates in the aquarium – dangerous for fish! ; How to deal with algae in an aquarium?
And how do you know how much of this evil is in your aquarium and how quickly it is growing? For this, there are aquarium tests for phosphates. I would recommend determining the concentration of phosphates weekly, then you can promptly respond to their growth and stop it. The content of phosphates in the aquarium water is determined using PO 4 tests. There are now many different ones on sale, both imported and domestic, both expensive and not so, both convenient to use and, in my opinion, inconvenient. Naturally, you want to buy not expensive and convenient.
Convenience of the test is a subjective concept. Therefore, after reading this material, everyone can decide for themselves what is convenient for them and what is not. Here I will provide all the information necessary for this decision and express my opinion, which is based on my extensive experience using aquarium tests.
Due to my job, I test up to ten or more water samples every working day. This takes a lot of time, so for me the criteria for convenience are a short test time and a minimum of manipulations with reagents and test tubes that need to be done during testing. I am annoyed by the narrow and tall cups for testing, which fall and spill, while glass ones are worse than plastic ones, since they also break. Measuring the required amount of water with a syringe is inconvenient. Measuring cups with marks provide no less accuracy of the test, but then you will only have to wash the cup, not the cup and syringe.
I compared several tests, using them to determine the phosphate content in real water samples from operating aquariums. Aquariums were chosen completely different: one with a dense fish population, and the other with a sparse.
However, first things first. First, I will tell you about the tests themselves.

UHE PO4 test

The kit includes 2 vials with reagents, two glass cuvettes (rather tall and narrow cups), a measuring syringe, a color scale. During the test, use a syringe to draw 10 ml of water into both cups. Then add 6 drops of reagent #1 to one of the cups, stir in a circular motion and after 2 minutes. add 1 drop of reagent #2, stir again and wait. After 5 minutes, compare the color of the liquid in the cup with reagents with the color scale, while the colors on the scale are viewed through the water in the cup without reagents. This water will act as a color-correcting filter for the aquarium water. Advantages of the test: cheap – 300-350 rubles; you can measure the phosphate content in the range of low values ​​0 – 0.05 – 0.1 – 0.2, which is interesting for planted aquarists who believe in the Redfield ratio; you can test colored water, but it"s unlikely to be accurate in the low range, which is where it matters. I"ll talk about whether this test is really that sensitive below. Disadvantages: cuvettes (they are also cups for testing) without graduation, so you need to use a syringe to measure out 10 ml of water, which are needed for testing; cuvettes are glass and not very stable, they can fall and spill when moving them along the color scale, and comparing the color of the sample with the color scale is possible only with the help of a second cuvette. That is, you will have to move both along the scale parallel to each other. The JBL company has implemented the same idea a long time ago (one of the cups plays the role of a corrective light filter), but it is done in such a way that the cuvettes-cups are placed in a special stand so that they can be simultaneously moved along the color scale, without the risk of spilling. When comparing the color of the scale not through the second cuvette, but without it, with the UHE PO4 test, the color of the sample is difficult to match with the colors of the scale, even if the tested water is colorless and does not affect the color of the test. The UHE scale does not allow measuring concentrations above 4 mg / l, which is not important for herbalists, but is important for fish farmers: in their aquariums there are 10 mg / l, and 10 is much more dangerous for fish than 4. The result should be expected in 5 minutes. Read the original instructions.

NILPA test – phosphate

The kit includes one measuring cup, one bottle with reagent, one container with powdered reagent, a convenient measuring spoon, a fairly large color scale with color samples arranged in a line. What is very convenient: you move the cup along the line of color samples and stop at the desired one. The colors are well distinguished from each other and are easily recognizable. Everything is very easy and simple. Advantages of the test: cheap – 300-350 rubles; works in a very wide range from 0 to 10 mg / l; convenient, easy to perceive color scale; convenient stable measuring cup (in the updated latest version of the test it is almost transparent); the test works quickly (the result is ready in 2 minutes.). When testing, you only need to do four manipulations with reagents: add 5 drops of liquid reagent to the sample and then, using a convenient spoon, add powder. Stir the liquid in the cup with circular movements. You can compare the color of the test with the color scale after 2 minutes. The instructions for the test say after 10, but practice shows that the color is completely set in 2. Everything is quick and easy. The test allows you to determine phosphate concentrations dangerous for fish up to 10 mg / l. Thus, the measurement range of this test is noticeably wider than that of others. Disadvantages: the inability to accurately measure phosphate concentrations in the range of 0.00 – 0.25 (in my opinion, this is not critical, since in a planted aquarium it is enough to ensure that phosphates do not exceed 0.25 mg / l, and even better, are less than the specified concentration, which this test allows you to do). You can still find the old version of the NILPA phosphate test with a circular color scale on sale, so I am providing a more convenient new scale here, where the colors are located in a line.

SERA Phosphat test (PO4)

The kit includes one measured cup (it is glass and can break!), two bottles with liquid reagents, a container with a powder reagent, a measured blade, a color scale, which is printed on one sheet of thin paper along with the instructions. The advantages of the test : accurate, samples of color differ well and easily recognizable answer is ready in 5 minutes. Flaws: narrow measurement range, only up to 2 mg / l, if you need to determine a higher concentration, you need to dilute the sample with phosphate-free water. This is unnecessary hassle. There are two liquid reagents here and you need to be careful not to mix up the order of adding the reagents: first 6 drops of reagent #1, then 6 drops of reagent #2. When closing the reagents, it is important not to mix up the caps, and they are the same! The spoon for measuring the powder reagent is inconvenient. The test costs about three times more than domestic analogues, but compared to other imported tests it is not expensive. The arrangement of the color scale on one sheet of paper together with the instructions is surprising, to put it mildly. Read the original instructions .

SALIFERT PO4 test

Advantages of the test: accurate and fast, a minute after adding the powder reagent is ready, a spoon for measuring the powder is convenient, an unbreakable cup. The test allows you to accurately determine low concentrations of phosphates. Disadvantages: inconvenient color scale: the color samples are small, despite the fact that they are separated by thick contrasting black lines. In my opinion, this makes it difficult to correctly perceive the color. For the sake of compactness of the scale, the color samples are arranged in the form of two adjacent rows, which is also inconvenient. When arranging the samples in a line, it is much easier to determine the appropriate color. You can measure only up to a phosphate concentration of 3 mg/l. To measure out the 10 ml of water required for testing, you need to use a syringe, and twice, since the syringe is only 5 ml. The test costs at least three times more than domestic analogues. Read the original instructions.

Tetra PO4 Examination

The Tetra phosphate test kit is extremely simple: one drop and one powder reagent, a measuring cuvette with clearly visible graduations, a convenient spoon for measuring out a portion of powder (NILP has the same). Advantages of the test: ease of execution, comparison of the test color with the scale is carried out not from above, but from the side. It seems to me that this is more convenient than looking at the test from above. Unbreakable cuvette and convenient color scale printed on thick paper – in this regard, the test from Sera is much inferior to the test from Tetra. In addition, Tetra PO₄ test works in a wide range of phosphate concentrations: from 0 to 10 mg / l. But the scale step is too large, which makes the assessment of phosphate concentration too rough. It is not suitable for herbalists. Disadvantages: too "wide" scale step: after zero value immediately goes 0.5, which, in fact, is the MAC for aquariums and ponds, that is, in the area of ​​low phosphate concentrations, the test is not accurate enough. However, in the range of medium and high concentrations, the situation is the same. Testing takes 10 minutes. This is long. The test is much more expensive than domestic and even some imported analogues, despite the fact that, for example, NILPA with similar configuration works more accurately and faster.
Read the original instructions.

And now the most important thing: we test the same water with all the phosphate tests described here and see what happens.
All tests, except Tetra PO4 Test, showed similar results. NILPA RO₄ phosphate test – 2 mg / l, SERA Phosphat-test (PO4) – similarly, UHE PO4 test – 2 mg / l or slightly more, SALIFERT PO4 test – between 1 and 3 mg / l (here it is – the inconvenience of their scale!) and Tetra PO4 Test. Here"s a problem: what color sample on the scale does the test color resemble? Probably 2 mg/l, or, still, 5? Decide for yourself. I redid the Tetra phosphate test several times and got this invariably incomprehensible result. Yes, the photo can be greatly enlarged if you click on it, then it will be easier to compare the colors.
However, 2 mg/l is a fairly high concentration of phosphates, and how will the tests behave when determining low concentrations? Now we"ll see. The photo below shows the results of testing water from a fairly healthy aquarium, the appearance of which suggests that there are no problems associated with excess phosphates here.

Samples of each test can be examined better if you click on the corresponding cup or near it. All tests, except SALIFERT PO₄ test showed similar results. UHE PO₄ test – solid 0.5 mg/l, NILPA RO ₄ Phosphate Test – between 0.25 and 0.5, but closer to 0.5 (click on the NILPOV dough in the photo to make sure of this!), SERA Phosphat-test (PO₄) – 0.5 mg / l, Tetra PO₄ Test – 0.5 or slightly less, but SALIFERT PO₄ test gave 1 mg / l. Who to believe? Salifert or all the others? As is known, questions of faith do not require proof. There are aquarists who believe in SALIFERT tests, no matter what others show.
You can check whether a particular test shows the exact value only by testing phosphate solutions with a pre-known concentration. It is not easy to make such a solution in the low value range without special laboratory equipment, so I used a ready-made one, like this.
The phosphate content in this solution is 0.2 mg/l.
And what happened? Here"s what: UHE PO₄ test, NILPA PO₄ phosphate test, Tetra PO₄ Test, SALIFERT PO₄ test showed a sonorous zero . And only Sera Phosphat-Test (PO₄) gave the right value – 0.2 mg/l.

Maintaining a healthy tank in your aquarium can be greatly impacted by selecting the appropriate phosphate test. This post will analyze the practicality, accuracy, and ease of use of several PO4 tests in order to compare how convenient they are. We’ll look at a number of solutions to help you choose the one that will best control the phosphate levels in your aquarium without causing you undue inconvenience.

So, the Sulfur test for phosphates can really determine a concentration of 0.2 mg/l, and it is the only one of the tests I have tested. This means that this test is primarily suitable for working with complex herb gardens and reef marine aquariums. But for servicing the vast majority of amateur aquariums, both with and without plants, in my opinion, it is most rational to use the NILPA RO₄ phosphate test.
After I wrote these lines, I tested the water from the herb garden with a very small number of fish (and, accordingly, very little food, a source of phosphates, was added there). The Sulfur test showed a phosphate content slightly less than 0.25 mg/l. But all the other tests (except for the Tetra test, which did not notice anything) confidently showed the same thing! Then why did they not work on the reference solution? Probably, the point is that it imitates sea water and the sensitivity of these tests in it turned out to be lower than when testing fresh water.
I diluted this water by half and determined phosphates in the diluted water using the tests discussed here. 0.1 mg/l was shown by the UHE PO₄ test and SALIFERT PO₄ test tests and only they. Thus, these two tests should be used in cases where the task is to determine phosphate concentrations in aquarium water that are less than 0.2 mg/l.
Well, have you made a conclusion for yourself – which phosphate test is better? You can discuss this on our forum in a special topic about phosphate tests . I also ask those aquarists who have experience testing water with a low phosphate content to share their observations.

Video on the topic

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