Do I REALLY need an air stone?

Most filters provide enough surface agitation to ensure adequate oxygen saturation. Bubble wands are really not necessary unless you've got a filter (or no filter) that provides little to no surface movement. They can be helpful in hospital tanks that use heavy meds along with a higher temperature, though.

As for the bubble wands, its not the bubbles themselves that add extra oxygen, but simply the surface agitation the bubbles create when they hit the surface.
 
As the other guys here are suggesting, you shouldn't need air stones except for specific cases. In my case, I use them in the hospital tank and the breeder tank where the bioload is close to nothing but still needs some water circulation...
 
Or coldwater tanks where oxygen isn't as abundant.
Bubblers have pretty much gone the way of the dodo, most filters have settings for current flow which adjusts the agitation and flow of the filter current.
 
I use airstones for a few reasons....

To get more surface movement when the filter does not do it enough. I like a lot of surface movement.

On several tanks that have a center brace the HOB filter is toward one end of the tank. I use an airstone on the opposite end to keep the water moving and keep things from settling into the gravel.

In general I find that having an airstone along the back helps keep the water moving throughout the tank and helps direct junk into the filter instead of settling to the gravel.
 
I have not used an airstone in decades. They make noise (and the pumps make more noise), mess up the cover glasses, and are not needed for current in an adequately filtered tank. All my tanks are well-filtered and the filters provide all the current needed.
 
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