clam snail issues
 

just bought a new clam but the snails are all over it eating the algae on it, Is this usually an issue and if it is what can be done about it

thanks in advance

Not likely a problem...unless you are unfortunate to have one of the certain types of snail that are specialist clam killers. If you obtained the snails from a shop that identified them, my guess is that it will be fine.