Common garden snails can do a lot of damage to succulents in a short period of time, snails can devour mesembs overnight. Snails and slugs are known to attack aloes as well.

Treatment of Snails:

Environmentally freindly:

Pick Snails off manually and crush them.
Pour salt over them but be careful the salt may damage the succulent.
Place a saucer of beer flush with the ground, apparently the snails are attracted to the beer and drown, this has never worked for me.

Chemical:

Kompel Snail Pellets sprinkled over the infested area, re-sprinkle the pellets when the others start dissolving.
Kompel Liquid snail poison, 60ml/10l water, repeated every seven days.
Carbaryl/Metaldehyde
Metaldehyde
Methiocarb