So he's out. He had to be cut out with scissors due to his belly bulging over the square. If I'd of used a knife or saw on the outside I'd of cut him for sure. When I got it out of the water I noticed there was a tiny gap in one corner of the square he was stuck in. So the scissors went in there I cut it and then had to gently twist the scissors to snap the square off. He's back in the tank after an our swimming about in a smaller tank. He's pretty battered though his tail is Tawney and his top fin including the thicker spikier parts are badly damaged.
Its a 50/50 chance at the moment but much better than the 0 last night. Thanks guys