Thanks to all for your comments and interest in dear old Bob.
Bob spent most of his time in the plant at the entrance to his tunnel, or in the tunnel itself. As time has gone on he seemed to age gracefully, and I found he would snap at the surface of the water whenever I appeared with food, as if he could not see it. I took to feeding him thawed blood-worms or brine shrimp, or live mosquito larvae using tongs so that he could grab hold of them. He also had his moist pellets but often seemed unable to see them, so I had to place them in the plant or his tunnel.
Over the past few weeks I was fighting to save Bob by treating him with
Myxacin as his fins just seemed to be getting shorter, as well as what appeared to be failing eyesight. He would still come out to see me whenever I appeared with his food. However, in the last few days Bob slipped off his plant and seemed not to have the strength to surface. I placed him in a shallow container, along with a live plant, that he was able to lie in, as his breathing seemed labored. Over the course of 24 hours Bob finally came to rest on the plant for the last time. He died peacefully this Monday evening (22nd July), and is now buried in the garden, which I felt he deserved after his time with me. RIP old fella, you were a good old fighter and started me off again having bought your first tank for a £1 at a car-boot - cost me about £80 to set it all up though. Bob was also well traveled as he accompanied me when I moved from the South to the North. I feel he is now at peace and felt I did the best I could for him, I would estimate him to have been about three years plus. Sorry to give you all this update, yet I feel he was as comfortable as he could be until the end.