I shouldn't think O2 would be a problem unless the tank is sparsely
planted or heavily stocked. Plenty of O2 comes in with each water
change and supplements whatever O2 the plants produce.

Lastly, "in my tank" I try to keep the surface agitation to a minimum.
I typically keep the water level, right up to the output of the HOB
filter, so the agitation is essentially none. The tank is moderately
stocked/planted with pearling common especially in the 1-2 days
following a water change. Pearling indicates O2 saturation of the
water, right? YMMV

I'd not worry about it until you notice your fish hanging out near the
surface of the water. Besides, I have always wondered if you can run an
air stone inline with the return water. People do it all the time with
CO2,,,,,, wouldn't O2 dissolve into the water just as readily? A simple
fix.

Just a thought. Good Luck.

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