This is actually pretty kickass! You've got a natural knack for being able to capture activity, too. Every picture of koi I've ever taken has sucked, cos they've all looked dead or completely disinterested.
I'm a sucker for Koi, I love feeding the ones at a local aquarium store all the time, fat B*stards that they are! My partner won't let me have one as a pet because not only are they big buggers as adults, but the 5 rats, 10 mice, 23 snakes, and several frogs, fish, lizards and turtles are enough for me right now!
Really cool motif If you look to the right you have the camera data for this image. There you see shutter speed and ISO speed. You could turn up the ISO to 1600 or more on moving objects and low light conditions (or use the corresponding automatic setting). I have no experience with the Nikon 5100 but some new cameras produce fairly decent images at high ISO rates without the resulting image looking too grainy.
this is going to sound weird, but is this taken in fort worth at the botanical gardens? o__O I have several pictures almost exactly like this. But I guess these koi are found all around xD but I haven't seen them anywhere to such a mass amount at once.