@Damage I thought part of it for me is I've seen many fish die for many reasons over the years, and I have assassin snails in my tank, which are weird little predators (that I put in specifically to eliminate the pond snail problem I had—it worked!) so I've seen what aquarium ecosystems can be like. But if you get them too, maybe it's just a thing? Maybe the brain is good at extrapolating that sort of potential future? (If that's true, how do polluters sleep at night?)