FWIW, I had a half dozen of these whelks in a heavily planted 20g long tank that was heavily populated with, (at the time), as many different species of shrimp, (actually more, I had a couple of the less common Neocaridina sp. that don't breed in fresh water, as well as some Green Lace Shrimp and Amanos in there), already heavily populated with MTS, pond snails, gammarus, etc.
I never noticed the assassins munching on any shrimp, (though it's entirely possible that they may have given the density of the plants and fauna). The tank also had four of those Clithon Nerites, though I never introduced any Ramshorns. Anyway, the Assassins never bred, so perhaps they were all the same sex, and though I was concerned about losing some of my Horned Nerites, they actually outlived the Assassins more or less, so it seems that Assassins prefer Ramshorns > MTS > pond snails > Nerites > shrimp. Please correct me if I'm wrong, or missing something.
It's fascinating watching nature balance itself. The transformation from what the tank originally looked like, with its myriad of plant and invertebrate species, to what it has become now. Overtime, left alone, the plants became an ever-changing under-water jungle, which has seemingly finally settled into what is essentially a massive thicket of (primarily) Subwassertang, though I did move a year ago and the tank is under significantly lower lighting than it used to be. It seems the flora in the tank were waging a war of their own, just as the fauna in the tank were/are. I wonder what it says about me that I find observing the behavior of snails so fascinating, especially given the fact that there are always fish/shrimp/crays/whatever that move around the tank at a much quicker pace! Any thoughts? I know I can't be the only one on this forum whose spent hours with their eye balls glued to the sides of their aquariums staring at their snails lol :nerd: