@rick I'm not a photo master, but from what I've seen, in order to make a good photo you need a sufficient amount of light, a good DSLR camera with big senzor, that can handle ISO 400,800 without noise, small F, and fast shutter speed of at least 1/200. Also, by using the blitz, the aquarium environment tends to lose some details but fish colors look more natural. Also, from my experience, I need 100 shots from which I choose 4-8 good photos. I'm pretty sure that professionals need less, but what I wanted to point out is that you really need to play with the camera and take lots of pictures. Also, luck and inspiration plays a big part too.
Happy fishkeeping everyone




