Are the reagents in the Hanna checker HR No3 and ULR Po4 affected by salinity?

[rennjidk]

Can they be used to test RODI source water and FW aquariums, or would the sample need to be brought up to target salinity?

 

[taricha]

The hanna PO4 gives unreliable results in RODI or freshwater.
The nitrate will work I think, but give a higher reading in fresh than salt.

In both cases they work pretty reliably in 50% salinity, so you can take the freshwater to be tested and mix 50/50 with some saltwater you know the parameters of, and figure it out that way.