The purpose of this post was to show how imprecise the home test kits.

I know I have issues and I am working on efforts to stabilize my tank. But because I have issues the short term solution is to test the parameters and make adjustments daily.

I was hoping that my use of test kits was precise enough to give me a close enough reading. Apparently not.

Now there are multiple ICP companies has anyone checked ICP results from different companies? I would be interested to see how close they would be from a single tank all taken at the same time.

Your coral doesn't care if your test kit isnt accurate. All it cares about is stable parameters every day. If you test Ca at 405 every single day (whether it's a correct reading or not) and you repeat consistent testing methods, then your coral will be happy.

Consistency over accuracy.

Anything else is just chasing the numbers.

Agreed to a point, however what if the readings you are getting off your test kits changes each time you test. Today you test the alkalinity at 7.0 and tomorrow you test it at 8.5 but it is only test kit error and the true alkalinity didn't change.

I am only searching for stable values not overly concerned if my alkalinity is 7 or 8 but I don't want it jumping all over the place.

A year ago I found out that my 6 month old Sybon salinity calibration solution was way off. I thought my tank was at 1.025 and it was actually at 1.030.

Sending off the samples to ATI is just a way of finding out if my test kits are giving accurate numbers.

Fair enough but how can you be sure ATI's results are correct?

I never got variable results when I tested with Salifert for example.

From what I have read ATI (German) appears to be the best. Triton North America had some early user errors, Marin Lab (Poland) is OK and Coralvue (US) is not reliable.

I am really not sure that you can even compare hobby grade test kits, that are wrought with human error to lab grade ICP testing done by a knowledgeable lab technician.

From my experience with hobby grade test kits they tend to be relatively consistent if we take out the human error factor.

I just wanted to know how my readings compared to the lab testing. I also wanted to confirm that there were no unwanted substance (heavy metals etc.) that cannot be tested for.