Put some air line tubing into the u-tube, about halfway and suck the air out. Once the water is flowing, put your tongue over the tube and slowly remove it from the u-tube. Suck slowly so that you don't get a mouthful of water!
If it acrylic then in a word, NO. Glass and acrylic are hard to get to bond together, there's a good reason why you don't see acrylic sumps with glass baffles and vice versa. And with the tank already being filled and stocked I wouldn't take the center brace off without tearing down the tank. If you dislike the look of the trim buy a rimless tank.