The honest starting point: your snail eats plants
A mystery snail is a large, hungry apple snail with a rasping mouth built for working over vegetation, and any planting plan has to begin there. Given a tank of tender plants and no other food, a mystery snail will methodically eat its way through the scape, starting with the softest leaves. The good news is that snails strongly prefer decaying matter and soft growth, so a well-fed mystery snail in a tank of genuinely tough plants usually grazes algae film and leaves the greenery standing. The planting strategy is therefore twofold: choose plants it dislikes, and feed the snail so it never has to go looking.
Plants with the best survival record
Anubias is the standout choice — its thick, leathery leaves taste bitter to snails and survive years of rasping attention, and because it grows on wood and rock, a snail climbing the hardscape never uproots it. Java fern earns its place for the same reasons: tough leaves, bitter compounds, rhizome anchored above the substrate. Established Vallisneria usually persists once its roots are deep, though new runners may be trimmed. A mature sword plant (Echinodorus) can hold its own, but expect the oldest, softest outer leaves to be eaten first and remove them before they rot. Marimo balls are often left alone and give the snail an interesting surface to graze across.
Plants that become expensive snail food
Soft stem plants such as most rotala, ludwigia and cabomba are eaten stem by stem, often floating loose within days. Delicate floaters are worse: a mystery snail hangs from the surface film and consumes frogbit roots and salvinia from below, and duckweed disappears entirely in a snail tank. Fine mosses fare mixed — Java moss is usually grazed rather than destroyed, but a large snail bulldozing through it loosens the whole mat. If a plant is sold as fast-growing because it is soft and lush, assume a mystery snail reads that as a menu description.
Feeding the snail off your plants
The single most effective plant-protection measure is a feeding routine aimed at the snail itself: blanched zucchini, green beans or shelled peas offered regularly, plus algae wafers and a calcium source for shell growth. A snail with a full stomach grazes leaves lazily instead of devouring them. Keep the tank covered, because mystery snails climb out to explore and to lay their pink egg clutches above the waterline, and leave a small air gap at the top if you would like to allow that. Remove any leaf the snail has skeletonised before it fouls the water. Watch the shell as your early-warning gauge: a mystery snail getting enough calcium and food keeps smooth, even shell growth, while a pitted or thinning shell tells you the snail is short on minerals and likely to turn even more attention on your planting. Plant choices shift as the snail grows larger and hungrier. For a candidate plant you are unsure about, put a follow-up question to KinsLe's Kimmy; she answers using the KinsLe Answers library.