I recommend not to get these, they look a lot like the black snails that you can find in the shoreline park in palo alto. I assume that they just found somewhere similar and took a bunch given the state they’re in from the photo
I feel like they’d be nasty or harbor all kinds of diseases. I also seem to remember they’re a different genus, ilyanassa or something, that’s invasive in our SF bay, and that’s also a cold water species that wouldn’t live very long in our tropical tanks anyway