I was thinking that, too, after I went to bed last night, bypassing the old plumbing and hiding a new hose behind the edge of the wall. Do you have the same pump for the falls and the fountain? If you do, that horrible noise might not be the pump itself, 'cause you'd hear it when the falls are running, right? (Edit: If I actually READ the whole post, I would have seen your answer.
My bubbler growls a little, too, especially when the flow is turned down, but it is disguised by the splash, so I don't hear it unless I am listening for it. If it isn't your pump, you can get a different head for your fountain that provides more aeration, for less than $30. It threads onto the same upright your current one is on, and they come in several different patterns.
I am not an aquarium keeper, but couldn't you run an airstone in there for aeration, too? I see you have power there on the right side (?)
Sorry to hear about your doggy. Mine is a pain in the rear, but I'd be doing the same thing.
Jen

I am not an aquarium keeper, but couldn't you run an airstone in there for aeration, too? I see you have power there on the right side (?)
Sorry to hear about your doggy. Mine is a pain in the rear, but I'd be doing the same thing.
Jen