"According to the API web site for this copper test:
The API® COPPER TEST KIT allows you to easily and accurately monitor copper levels to maintain copper-based fish treatments at therapeutic levels, and tests copper levels from 0 to 4 ppm."
This test can only read between 0 and 4PPM. Most fertilizers on the market only supply 0.001PPM. And the EPA limit for tap water is 1.3PPM. I don't know what Ireland coppers standards are but I doubt there levels are higher than EPA limit.
I would advise you to save your money and not buy this test. The ICP-OES test I mentioned will detect copper down to 0.001 and will probably read above 1PPM. I have never seen copper levels that high but it will easily read calcium, magnesium, potassium, and phosphorous levels way above 1PPM. No standard aquarium test kit will provide you with as much information as one ICP-OES test will do.
I have used this test and I have Nerites in my aquarium. So at a minimum we could compare your tank water with the test result from my tanks.
ICP-analysis.com test kit on Amazon.