This is one of those shots where you have to juggle shutter speed and light. I think, if the light had been brighter, this would have scored better (dropping shutter speed might have blurred the fish). A background of a complementary color to the fish would have made this image eye catching - right now all the hues are too similar to stop people in their tracks. That effect works for moody images, but this image isn't moody. The smudges and the blown out rings on the bottom do detract but I think they could have been overcome with more contrast in hues - a yellow background would have made this really pop.
this would be a better shot if there wasnt a big finger print smear along the rim, and then you can see the shadow and the ring below the bowl of the glass is really blown out,
just to add, it would have been cool if you took a mirror and used it to work up the beta so that he would be all swolen and in defensive mode,