They don't really eat them, correct. Instead they force the bacteria to produce new phages until it explodes under internal pressure and dies. Plus, phages are

They don't really eat them, correct. Instead they force the bacteria to produce new phages until it explodes under internal pressure and dies. Plus, phages are viruses, unlike roundworms and the like, they can survive centuries without food. They also, as mentioned, account for 30% of death in marine life every day, biggest killer organism on this planet. There is phage-therapy too, an alternative to anti-biotics, where you are given a dosage of phages in an infected area. Due to their nature they only attack specific strains of bacteria and can easily eradicate the entire population within a few hours.