Historical clue formulations

• Dirty film — 2026-04-26
• Dirty film — 2024-08-25
• Film about fish tanks? — 2022-11-25
• Floating green layer — 2021-03-05
• Buildup in a fish tank — 2020-09-01
• Riffraff — 2017-01-08
• Lowest of the low — 2015-07-31
• Lowlife — 2013-08-27
• Dregs of society — 2012-12-23
• It may be found on a tank — 2012-11-22
• Disgusting film — 2012-06-29
• Dirty film — 2012-03-31
• Cleaner target — 2011-10-02
• Film you don't want to see — 2010-11-07
• Pond film — 2010-01-13
• Refuse — 2009-10-25
• Pond gunk — 2009-01-19
• Cleaning target — 2008-04-05
• Soap ___ (shower buildup) — 2006-05-31
• Ugly film — 2006-01-26
• Pond gunk — 2006-01-23
• Lowlife — 2005-09-05
• Pond gunk — 2004-04-27
• Film on ponds — 2003-04-09
• Riffraff — 2003-03-22
• Society's dregs — 2003-03-09
• Riffraff — 2000-11-12
• Lowlife — 2000-01-06
• Riffraff — 1999-03-19
• Riffraff — 1998-04-30
• Refuse — 1998-03-31
• Pond dross — 1997-06-27
• Spray cleaner target — 1996-02-06
• Lowlife — 1994-08-07