As Lebron stated, the outflow of the filter is tyically enough. If you put your water line a little below the output of the filter so its more of a waterfall you're water will be oxygenated more than enough. Most people don't add the additional aeration unless they have their temp really high or a deep tank. I have a 46g bowfront with female Bettas, snails & 2 CAE's & I only have the canister filter & everyone appears healthy & happy.