bottom feeder vs seaweed

bottom feeder

noun
  • A fish or other aquatic creature that feeds off the bottom of its habitat; a flatfish. 

  • A person who operates amidst or thrives on the unwholesome things in a society; one who takes advantage of the misfortune of others. 

seaweed

noun
  • Any of various fresh water plants and algae. 

  • Any of numerous marine plants and algae, such as a kelp. 

How often have the words bottom feeder and seaweed occurred in a corpus of books? (source: Google Ngram Viewer )