feed off something—
1. use smth. as food:
- Blacktip sharks are reef sharks; they feed off fish living in the coral, and are not interested in big mammals.
2. use smth. to advantage (usually with negative implication):
- They feed off our desire to smoke and the miseries of our lives that caused most of us to start smoking.
feed on something—eat certain food as one’s regular diet:
- These sharks are bottom dwellers, in nature they feed on fish and shellfish that they suck out of the sand.