Is KDF 55 or 85 okay?

[hsd94]

Hey Guys -

This question is for the water experts out there -

for a freshwater system is it okay to use KDF 55 or KDF 85 in my pre filters?

Stage - 1 sediment
Stage - 2 0.5 Micron Carbon
Stage - 3 (Catalytic Carbon with a few pounds of KDF 55 or 85)

any possible harm?
Thank you!!

 

[Reefing Madness]