Okay Okay, I am the inherited owner of this fish and there are many things to explain before you lot jump to even more conclusions......
1st - Harry is AT LEAST 18 years old!!! So he isnt doing too badly.
2nd - Harry used to belong to the mother of one of my lecturers at university. When she died, nobody wanted him or Humprey The Catfish (that's right, not even her sons) so I took the little fella's.
3rd - you all seem to be saying that he is "deformed", i would like to point out that he was this way when i inherited him 3 years ago.
4th - the tank (which came with the fish and they have lived in for all their lives) is pretty big, much bigger than you see from the photo.; its at least 250 litres
5th - they have a fully working filter and new double-airation pump.
6th - the reason the tank seems so grim (which is the reason for me posting the problem on the forum as i needed some help) is because last week I moved house and i moved the fish with me. Before we moved, they were perfectly happy, regular water changes, lovely clean tank, happy fish (thank you very much!). When i moved i did a full clean and changed some of the water. Clearly this is how the problem has arisen as I have over cleaned and removed to much good bacteria. I am aware of this now and I thank BOD for all his helpful advice.
7th - thank you for your identification of my fish, I am glad to know what he his. It's a shame you all think he is not very pretty though......i don't help fish because they are pretty but because they needed a home.
Hope that clears a few things up!