The curved horizons of the upper and lower (red) areas are telling me that you are using a very wide angle lens, 17mm or less, or being to close with a regular wide angle, 35mm. Try to use a longer focal length of at least 50mm or move back a little. The green area, scratches?
Of course, always clean the glass inside and out before photos and a tripod can be handy. The focus is just a little soft, but acceptable for a smaller image.
The lighting is great, just the tank lights?
What type of camera are you using?
It has that wide angle look because it is a bow front tank. Could that be what you are talking about? As for the "focal length" how do I change that? Also what do you mean about focus is a little soft? How do I correct that? It is a cannon Power Shot A80. Any suggestions would be great.