Historical clue formulations

• Something consumed by the ton by whales — 2026-06-28
• Filtered food for whales — 2026-04-20
• Filter feeder's fodder — 2021-09-03
• Whale food — 2017-09-24
• Food filtered from seawater — 2006-05-27
• Crustaceans eaten by whales — 2005-10-25