Historical clue formulations

• Bloom that's green — 2025-12-31
• Growth in a fish tank — 2025-11-17
• Unwanted growth in fish tanks — 2025-07-06
• Pool owner's problem — 2025-05-16
• Pond buildup — 2023-05-02
• Buildup of tanks? — 2023-03-15
• Fish tank buildup — 2022-09-18
• Growth from stagnation — 2022-01-29
• Pond scum, typically — 2021-10-05
• Fish tank buildup — 2021-05-18
• Aquarium buildup — 2020-01-14
• Tiny pond plants — 2019-11-25
• Fish tank film — 2019-05-26
• Seaweed, e.g. — 2018-12-17
• Growth on buoys — 2018-09-21
• Fish tank gunk — 2018-05-14
• Fish tank buildup — 2018-04-03
• Aquarium buildup — 2017-12-18
• Fish tank buildup — 2017-07-31
• Simple pond life — 2017-03-20
• Organisms that cause red tide — 2016-03-14
• Pond growth — 2014-06-17
• Food for tadpoles — 2014-04-24
• Phycologist's study — 2013-07-21
• Tank top? — 2012-09-02
• Biofuel source — 2012-06-03
• Seaweed, e.g. — 2011-05-24
• Pond buildup — 2010-06-08
• Potential pond poisoner — 2010-05-28
• Fish tank buildup — 2009-12-16
• Red ___ — 2009-04-18
• Pool owner's nuisance — 2008-02-29
• Aquatic plant life — 2008-02-18
• Aquarium buildup — 2007-02-25
• Aquarium problem — 2007-01-18
• Tiny pond plants — 2006-09-25
• Pool problem — 2005-11-03
• It may fill up your tank — 2004-07-31
• Pond buildup — 2004-05-03
• Pond growths — 2004-01-26
• Plankton components — 2003-09-28
• Pond buildup — 2003-07-28
• Plankton, in part — 2002-02-15
• Pond cover — 2001-04-25
• Low end of the food chain — 2000-09-18
• Seaweed — 2000-05-08
• Frog spit — 2000-04-15
• With fungi, they form lichens — 2000-02-17
• Certain thallophytes — 1999-10-10
• Sea drifters? — 1999-07-10