WATER TESTING: HOW TO USE TITRATION TESTS

Many water values ​​in marine aquariums are determined using colorimetric and/or titrimetric tests (better known as droplet tests). These tests are easy to use and can also be used by non-chemists. Despite all this, there are a few things to consider. We have put together some important tips for you.

In the carbonate hardness test, the concentration is determined by the number of drops that must be added until the color changes from blue to orange.

What should you pay attention to when buying droplet tests?

The water test should in any case be suitable for sea water.

Also consider your "aquarium" goals when making your purchase decision. Do you only have robust soft corals, zoanthus and lots of fish in your aquarium? In that case, a test with a high measuring range and lower accuracy may be sufficient. On the other hand, do you keep more demanding hard corals and your nutrient levels are generally very low? Then choose a test in the low measuring range with high accuracy (e.g. Pro versions).

7 tips for using droplet tests

#1 Check the test

Before you even start, first check the best-before date (BBD) of your water test. The reagents in the test kit can actually expire and become unusable. If the expiration date has long since passed, we recommend that you discard the test. Alternatively, or if it has only been passed for a short time, it is a good idea to check the water test with a standard solution and, if necessary, determine a correction factor. This way you can use the tests even after the best-before date.

Always store your water tests in a cool, dry place to extend their shelf life.

#2 Be meticulous and accurate in your water analysis

In order for the test to show the most accurate measurement results, it is important that you:

• follow the instructions exactly
• Waiting times
• work cleanly
• Reads sample quantities from the syringe and not from the cuvette
• Dosing powdered reagents with level measuring spoons instead of heaped
• Do not hold the dropper bottles at an angle but vertically so that the droplet size remains constant
• drip the reagents into the sample and do not let them run along the wall
• If there are several plastic syringes in a test kit, label them accordingly so that they cannot be confused

Only those who work cleanly and precisely can expect exact measurement results.

#3 Pay attention to the time of the measurement

Always test your water values ​​at the same time of day. This is especially important for the pH value, as this changes throughout the day.

Logically, you should not take water samples immediately after feeding. This would distort the results.

Give yourself some peace and time for your measurements. Hecticness and stress can quickly lead to measurement errors.

#4 Improve your color perception

It can sometimes be difficult to correctly assign the color of the sample on the color scale. What can help here is a good light source. Some tests also include a so-called comparator block. In this block, a sample cuvette and a comparison cuvette (sample only, without reagents) are placed. The comparison cuvette is placed above the color scale in such a way that the color impression of the sample cuvette is imitated, thus simplifying the comparison.

#5 Use a reference solution

A reference or standard solution contains precisely set concentrations of a substance such as phosphate, KH or nitrate. By testing with a standard, you can check the functionality and accuracy of a test. It is particularly useful after long periods of storage and when unexpected measured values ​​are present. If there are deviations from the target value, a correction factor can be determined using the reference solution.

With reference solutions such as the NP standard from Tropic Marin you can check the functionality and accuracy of your water tests.

#6 What to do if the concentration is outside the measuring range?

In this case, you can either double the sample amount or dilute it with osmosis water. The result must then be divided by 2 or the dilution factor.

Theoretical example: You measure your nitrate level and notice that the pink color is even darker than the color of the last field on your color scale. Your color scale ends at 20 mg/l. Your nitrate level is therefore above this. You repeat the test. Instead of 5 ml of sample water, you fill the cuvette with 2.5 ml of sample + 2.5 ml of osmosis water. Your dilution factor (amount of initial solution: amount of final solution) is 0.5. You can now read 15 mg/l on the color scale. You then divide this value by 0.5 and thus know that your actual nitrate level in the tank is 30 mg/l.

#7 After the measurement is before the measurement

Handle your equipment carefully and rinse the cuvettes thoroughly (ideally with osmosis water) and let them dry. It never hurts to always have a spare cuvette on hand. The little things can easily fall down and break.

And now: happy testing!