Mystery snails are among the easiest tank mates to combine, because they simply do not fight. Two snails will graze past each other, cluster at a food wafer and occasionally climb one another with no harm done, so the limit on how many you keep is set by the tank's resources rather than by the snails' tempers. As a working guide, allow roughly five gallons of well-filtered water per snail, then adjust by what you actually see: shells growing smoothly and snails active across the whole tank means the balance is right.
Feeding a group that cannot live on leftovers
The persistent myth is that snails maintain themselves on algae and scraps, and in a group that myth starves snails in slow motion. Each mystery snail needs its own share of sinking food, vegetables and a calcium source for shell building, and in a planted community tank the fish will reach most offerings first. Drop food in more than one spot so a slower snail is not fenced out by its own companions, and check shells as your feeding report card: smooth, even new growth at the shell edge says the diet and water are supplying enough, while pitting and a ragged growing edge say the group is underfed or the water is too soft and acidic for shell health.
The egg clutch decision
Keep a male and a female together and you will likely find a pale pink cluster of eggs glued above the waterline, under the lid where the air stays humid. A single clutch can hatch into a great many tiny snails, which is charming exactly once if you have no plan for them. Decide your policy before the first clutch appears: leave the waterline space and humidity if you want babies and have homes or shop credit arranged, or remove clutches promptly and keep the water level higher to discourage laying. Sexing mystery snails is fiddly, so anyone keeping two or more should treat clutches as a when, not an if.
Space, lids and tank mates for a snail group
Mystery snails wander, climb and occasionally explore beyond the water if a gap invites them, so a group needs a secure lid and an escape check as part of the routine. They do best with peaceful fish, since curious nippers learn quickly that snail tentacles and siphons are worth investigating, and a snail that stays shut all day in a tank of lively fish is telling you it feels hunted. Give the group surfaces at every level, grazing film on wood and glass, and enough floor room that several large adults are not constantly bulldozing the same corner, and they will reward you with constant slow activity.
A record for each shell
In a group, individual snails blur together until something goes wrong, and then the details matter: which snail's shell has gone thin at the edge, which one arrived with the chipped spire, which has been shut and floating for two days while the others graze. Photographing shells when snails arrive and noting growth, clutches and quiet spells builds the history that separates a normal rest from a decline. Those notes belong with the animals rather than in a camera roll, and KinsLe's Pet Passport keeps each mystery snail's records together in one portable packet that is ready for a vet conversation, a tank upgrade or a move to a new keeper.