Will this gap allow enough oxygen into the tank?

[Ryan_F]

I cut a new piece of glass for my 20gal because I’ve had a fish jump out and have been paranoid ever since. Just wondering will the gap allow enough oxygen into the tank because I don’t want them to suffocate. There is also a small gap near the heater.

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[Colin_T]

Have you got an airstone bubbling away in the tank?
If yes, then that gap is heaps.
If no, then that gap should be adequate as long as the power filter is creating some surface turbulence.