Evaporting 2 gals a day! Wow! Poor fish must be boiling. :-)
Seriously, water filtering/management could be a problem and some different methodolgy involved could be a good solution (if you haven't already do so) if you must put a speaker above your tank. And, if you can do it, it will also reduce the noise level from motors/filters and air bubblers substantially in the room and/or tank.
I had a 160gal tank for salt water fish and crabs etc and took my filtering out of the room to the garage. Not only did it quiet everything down it made routine water changes a walk in the park. If your set up allows this, think hard about it. Its really worth the effort, especially if you are tying to keep sensitive species thriving AND not losing the benefits of a high quality audio experience.