[Samw]

It depends on the skimmer. Most skimmers have water pumped into it (from outside the skimmer) and thus the water that returns to the tank is oxygenated well. However, closed loop skimmers like the smaller Tunze ones and of course Co-current airstone ones do not force water into it from the outside and thus the oxygenated water is very slow to return back into the tank and so your tank does not get oxygenated. Powerheads alone do not oxygenate very well unless you attach the venturi to it but that will cause too much salt spray.

I've done lots of tests with my oxygen meter to verify my claims and there is an article on RC about this.

Previously, I tested oxygen levels in my 38G tank with powerheads running and the Tunze Nano skimmer on. Within a few hours after turning off my lights, my oxygen level was below 40%. After replacing the skimmer with a Remora, my oxygen level is now 85% for the same tank all else constant. I don't believe that the powerheads made any significant impact on oxygenation in my tank with the way it is set up which is to circulate the water near the surface. I believe oxygenation in my tank at night is solely handled by my Remora at this point. I am so confident in my system now that I restocked my tank with Acroporas and Birds Nests which I could not keep before.

With your Prism, I am making an educated guess that it is enough to oxygenate your tank assuming that you don't have a gigantic tank. Air pumps won't be necessary but an emergency one that turns on automatically when the power goes out will be useful to have. Powerheads might make an impact if you have the water returning above the waterline so that it splashes. I've never tested that with my o2 meter since I don't think it is practical for me to have the salt water splashing and spraying.