Ive not had any probs with platys (and other livebearers) mixing with my neon tetras. They even lived in a largish tank with a betta and didnt nip. You'll just have to keep an eye out
That's good to know they're both compatible. But my LFS discouraged me because of their ph differences. So, how did you guys manage it, met halfway what's tolerable for both? I love the cardinals but didn't get for the ph reason.
It makes a change to see a LFS that takes things like pH into account. Let's just say that mine didn't.
In my case, I have a reasonably high pH at 7.8 - I can only assume that my Cardinals are captive bred, and thus a little more tolerant of a different pH.