Nerite snails...after seeing George Farmer talk about the one in his nano tank, I bought some for my 54L. They've been in for 3 weeks now and slowly but surely the algae has all but gone. The glass and pebbles are pristine and the plants have also had a good going over aswell: I think that these are amazing little creatures, the algae being eaten off the glass and pebbles seems to stop it developing on the plants as quickly.