Red Leg?

[Louis Charles Bruckner]

if you are worried about water quality just take a new ziplock sandwich bag with some of the aquarium water to you local pet store
a small mom and pop store not a petco or petsmart
they will be happy to test your water for you and they have done the tests many times and rarely make a mistake.

Bottom line if you keep good water quality and don't over think things.
your frog will be fine.