Normal Oranda Behavior

We just got an Oranda a few days ago. I have another goldfish with him, along with a dojo loach. The fantail swims around all areas of the tank. The oranda goes to the top and stays there for a while, and it looks like he is "blowing bubbles". Probably just gulping air, I am not sure.

Is this normal? Here is the info on my aquarium:

28 gallon, with bio filter that filters 200 gph.(should be plenty,right?)
Nitrates- 5ppm
Nitrites- 0
Ammonia-0

I don't have a bubble curtain in there yet(we are putting in one this week). I don't think they are not getting air, there are air bubbles all throughout the aquarium, and the filter seems to keep it really fresh.

It doesn't look like a swim bladder problem, and the other fish are not doing the same thing. Any thoughts?

Thanks,

Cecileew