For high quality fish feed, the ratio is 2:1. Two lbs of feed puts on a pound of weight on the fish.

For fish eating other fish, the ratio is 10:1. Fish needs to eat 10 lbs of fish to gain one pound of weight.


Excerpt from Robert Crais' "The Monkey's Raincoat:"
"She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."