Is a Air Pump necessary?

"Lee Brouillet" writes:

I must (respectfully) disagree with you on this, Sam. By the time the fish
are hanging out on the surface or at the waterfall, they're STARVED for
oxygen, which is nearly too late. Why wait that long? They will grow better
and be much happier with adequate O2 in the water. Mother Nature pulls a
dirty trick on fish: in the summer, when they're the most active and
growing, she yanks the oxygen out of the water because it's warm. Think of
it like trying to run a marathon in Denver without training for it . . .
sorry, there's just not much O2 in the air up there G. Same thing: not
much O2 in warm water. Aeration is like filtration: you can't get too much.

There is a saturation point for oxygen dissolving in water.

For filtration I agree, just because if its twice as big it needs to be cleaned
half as often.