FWIW, I have not the greatest confidence in the hanna having recently had some pretty wonky readings from different reagent bottles (neither were close to expiration). Hanna had generally read pretty consistently about 0.5 dkh higher than trident. Then all of a sudden its reading 1.0 dkh lower than trident .... replaced the non expired reagent and now it’s back to about 0.3 dkh higher. I suppose the good news is that my tank looks fine at either reading LOL.