Of, relating to, or having the nature of conferva; resembling scum or algae.
From Latin confervosus (slimy, algae-like), derived from conferva (algae, scum). The suffix -ous makes it an adjective meaning 'full of' or 'having the quality of'.
Before modern germ theory, 'confervous' waters were simply thought ugly—nobody imagined that these microscopic organisms were both essential to aquatic life AND sometimes lethal to drink.
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