I am not sure I would ever buy another trident with being on my 5th in 3 yrs. They are cheaply made and hell they can’t even give calibration fluid that tests at the levels on the bottom. Sent in one for icp testing to ati and it wasn’t even close not to mention all the hanna salifert red sea test kits I have used to test their “dkh” levels and it’s usually 1-1.5dkh off