HazelNuts, the great majority of gliders carry water in their wings only, but there are a few that have tail ballast as well. Tail ballast does affect the AoA and therefore the L/D.
Capn Bloggs, Please don't make the mistake of thinking that Professional Pilots only fly large jet aircraft. There are a large number of professional pilots around the world who only ever fly light aircraft, and even a few professional glider pilots.
