Thanks guys.
Grins, the donut is a sea squirt of some type, very hardy have had him almost since day one, was the inspiration for coming up with a design not to overflow the display. He managed to get into the overflow, up the tube, and then down getting wedged where the bulk head is. He was too far down to get from the top, so had to undo the bulkhead from the bottom. Had a friend staying over that weekend and she is like really tiny, I still can't get the image out of my head with her gripping onto it with both hands under the tank while my wife and I tried to pull her and the squirt out as it was really, really wedged tight.