Are test strips enough or are liquid tests necessary?

[VladVenger]

I read through the forums and the liquid test kits seem to be more accurate, but are the test strips good enough accuracy wise?

Any you could recommend?

 

[StevenF]

IN my experience with liquid test and strips (I use tetra 6 in 1 test strips). both are reasonably accurate. I use the term seasonably accurate because the accuracy is entirely dependent on ones ability to distrtinguish color. The ability of people to distinguish color series and is also impacted by the lighting spectrum.

For example a person that is color blind cannot use most tests. Also don't read the test under a low pressure sodium vapor light (it has a very low color rendering index). Most indoor lighting has a CRI of 80 which is acceptable but For best result always use indirect outdoor light to read a test.Be careful to follow the directions correctly. Test strips only need less than 0.1ml of water per pad to perform there work. Many people leave it in the water too long or carefully remove it horizontally trying to keep a maximum amount of water on the strip. The correct way (at least for tetra 6 in 1 test strips) is to push it in vertically and then yank it out of the water vertically after no more than a half second. Then wait a minute for the color to develop and compare it to the chart. For liquid tests verify your chemicals have not expired.

If you look at most liquid test kits no accuracy specification is listed on the label. The few tests that do lis an accuracy operate differently and are called titration tests. In these tests you slowly add a chemical through a stringe (drop by drop) until a visible change occurs (color to transparency). At that point you stop and measure the amount you added and then use a table to determine what the concentrations is.

The Most accurate test available to hobbiest are ClorImeter tests:
http://hannainst.com/products/checker-colorimeters.html
IN these tests a photometer reads the color of the sample and a computer converse that to a number it displays. They range in cost from about $50 (checks for only one water parameter) to about $1000 (able to check for multiple water parameters)

Another New option I have not tired are JBL test strips. They work like the tetra 6 in 1 test strips but you can download an app for your phone. The app uses the camera in your phone to read the strips.

 

[StevenF]

Note you can verify the accuracy of any test using a 1 liter of RO or distilled water, a dry chemical, and a milligram scale. For example measure out 10mg of potassium nitrate and add to the 1 liter water botle. Then test the water with your test kit. it should read 10ppm. 1mg in 1 liter of water = 1ppm.

I did that for nitrate on the strips I use. I also used hanna colorimeters and compared the results with liquid test kits. I did that for alkalinity and phosphate. For PH I purchased a PH meter and calibrations solutions for it. The it was working (I need to get it repaired) it confirmed the strip PH reading. After installing a RO system at my sisters home I tested the water with my strips and she sent out a sample to a free lab (Unfortunately the lab only tested for PH (but it was feee) and it agreed with the strips.300ppm for the strips and 270ppm for the lab.

Note I also tried the tetra ammonia test and I don't like them. IT is possible to get a false positive for ammonia and it has a low resolution color chart and I find green is the hardest to get a good match to the chart. I now use a hanna colorimeter for ammonia.