This guy just poses naturally, he pretty much moves in slow motion and holds his poses for the camera so photos of him are quite easy. My other guys are hard to do though
I only recently discovered how to make black backgrounds like that, basically you just raise the f stop so the camera can only take black photos and then use the flash to illuminate the fish only. Very easy and you dont even need a black background for it because the camera thinks everything is black.
The hard part is figuring how much flash you need to use, so theres a bit of trial and error before you find the right settings for your fish...only problem now is that Ive messed with the settings and cant remember what ones I used to take normal photos...so Im going back to trial and error again haha