when i used api, i am able to 100% confirm that they are inaccurate. how do i know? well, i was able to confirm with 2 additional test kits.
ammonia-always reads .25 where as a red sea kit will read 0, and also confirmed by an LFS.
nitrite- the last time i cycled a new tank, my api kit tested .5. the LFS used an api kit and it tested 0. my red sea kit tested 0.
phosphate-apit kit is horribly inaccurate. reads .25 or more when there is less than .02.
ive also had api kits not even change color with regards to a nitrate test, which is obviously wrong, and was confirmable by doing a red sea test.
they are good starter kits, but if accuracy means anything, for the person using it, the readings should be taken with skepticism