Define "Aeration"

I have a quick question, I want to get a powerhead for my 72 since I dont think I have enough surface agitation. Does the water have to acually "break" and splash or can it just make tiny ripples in the surface for gas exchange?
 
I have a quick question, I want to get a powerhead for my 72 since I dont think I have enough surface agitation. Does the water have to acually "break" and splash or can it just make tiny ripples in the surface for gas exchange?

ripples are usually enough
 
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