Cut about 1/2” to 3/4” and working perfect now!The farther down you cut it, the more splash from the overflow making it noisy.
There is a sweet spot, 1/2" to an inch below the weir. Clears the tank of the film and quiet. All the flow you need.
Did they seriously glue it in the bulkhead?
Doesn't need to be.
Did you try and pull it out?
I don’t think it’s glue I think it’s ptfe tap