All are perfect. The sentence "I breathe air" is correct but it sounds biological. It is so obviously true that you would never have a reason to say it. It would be like saying "I have teeth" or "I live on the planet Earth". Of course you breathe air! However, "I breathe the air" is something you might actually have reason to say. Here are some examples: "I breathed the air in that room and something smells fishy." "It is such a beautiful day that it makes me feel good just to breathe the air."

1. ‘Fishes’ is the plural when you are referring to species of fish. You should use the plural that corresponds to your meaning. 2. You need to use ‘the’ if you refer to specific air. People breathe the air that passes through these filters, so the filters must be regularly maintained.

The air most generally refers to the atmosphere all around us. It's a single specific thing, so we use the definite article. And also, because it's a little abstract, like the earth, the sea. We're talking about the totality of that element.

Hey Tablo! You can say fish or fishes, it's not important which you use for the plural. Your sentence is good. You can say "I breathe air" for a general statement; "I breathe the air" sounds more like poetry or song lyrics. You can say something is "nonliving," since it's an adjective. However, I only saw this word for the first time recently in an ESL textbook! I think most native speakers would rather use "inanimate" instead of "nonliving" (But that's just my opinion!).