Aqualung was re-released in a 40th anniversary edition on 31 October 2011. The release contains a new stereo and 5.1 surround remix of the album by Steven Wilson, and comes in three different editions—a “collector’s edition” containing the album on LP and two CDs, as well a DVD and a Blu-ray disc (with better sound quality than the DVD) and a hardback book; a “special edition” containing the two CDs and an abridged version of the book; and an “adapted edition” containing two CDs (with 2 extra songs not included in the other two 40th anniversary editions) and 2 DVDs in a hardcover book (written content is the same as in the Collector’s Edition book, only the Chronology differs slightly).
“Jethro Tull’s Aqualung is … a masterpiece, but was sonically a very poor-sounding record. So, some didn’t rate it as highly as they should have. What we did with Aqualung was really make that record gleam in a way it never gleamed before. I think a lot of people, including myself, have come around to thinking that the album is a lot better than they even gave it credit for previously. So, there is certainly something very gratifying about being able to polish what was already a diamond and making it shine in a way it never has before” – Steven Wilson
Additionally, according to mastering engineer Steve Hoffman there were tape stretching problems with the original session mixdown master, implying that many editions of the album used multigeneration copies as their source.