I thought of puttin 4 or 2 LEDs at the end of ech of the tubes.(Water still in them) and lightin them up or make something that makes them blink.
I think it would be better to leave the plastic pipe and just cut a retangular opening about midway. Cover the hole with fiberglass or metal screen. Putting fan on both ends is gonna move LOTS of air. A same built tube on the other side of the case could be the intake while the other is the exhaust. But just drilling holes in the tube will make it whistle.