Other contributors have said "What are the animals you use as sources of food?" is the same question as "What animal uses algae as food source?" If you believe that these are not asking the same thing and should be answered differently, click here
If you are a vegetarian then you do not usually eat meat (animals) but if you are not a vegetarian then you eat meat (animals) some meat that's good to eat is chicken, steak(cow) ham, pork, fish,...