I’ve been there- taking a dead snail out is perhaps the worst smelling experience, maybe even worse than a dead coral. The smell just lingered in my nostrils for days. I just couldn’t forget…Well the first tank death is confirmed. The Trochus/Astrea still hadn’t moved when I checked this morning so I gave it the sniff test again. My god that was an experience ;Vomit
Sometimes these snails just die for some reason. I usually buy them in bulk so that at least a few survive.