That's an awesome shot! I had no idea how difficult it was to shoot fish until I tried - and out of 3,000 photos on my flickr site, none of them are fish
The air bubbles really add another dimension to it, and you nailed the focus. I really like working with extension tubes myself, but you must have been quick to get this shot!
The bokeh in my photo was actually made from a fountain. It's one of those that had a small bowl at the top that spills into a large bowl at the bottom. I was sitting on the edge of the large bowl. The light had to hit the water at exactly the right time and at the right angle to the camera to make the effect.
I have absolutely no idea what I'm doing with flash, so no, no flash on this one.