Hanna marine pH tester with freshwater

[swbrenneis]

I use Hanna test kits for my reef tank and am very pleased. I would like to get some Hanna kits for freshwater, but all of the testers on their site are geared toward swimming pool tests.

Does anyone know if the Hanna marine pH tester is accurate for freshwater as well? I have compared it to the freshwater API kit and it seems close, as far as I can tell. The API pH test color gradient is awful. pH is pH, freshwater or saltwater. I just don't know if the reagent would be the same.