u/FollowNubly

I have two black Tetras in a shoal with a school of 6 Neon Tetras. I'm now aware this is non-ideal, I did it on the recommendation of the pet store owner, they told me they would school just fine with the neons as if they were neons. For this reason I'm thinking it's stress spots (And that's it's ONLY on the black Tetra), but it's too late to return the Black Tetras and I'm unsure of how to rehome them.

Aware the water is on the hard side, I originally used city water but I'm now using RO, it's getting softer with every water change.