u/Attarite

I got these guys as hitchhikers from some dwarf water lettuce when they were babies. I scooped this one out for a good photo of the transparency of his shell near the aperture. I tried researching on my own, but nothing I found was conclusive. Is this a water parameter issue? Genetics? Totally normal?

Water parameters:
Ph-6.4
Ammonia- 0ppm
Nitrites- 0ppm
Nitrates- 20ppm