@Edvet: yeah, your picture is about right. We have used towels and tried to scare the fish, so they suddenly stash to the center of the tank, wait for couple of seconds and they swim back quickly. As you can see in all photos the school heading to right side, it's where they decided to "hide", so our job before each shot was to make them swim to center and then wait they swim back. So, I held one flash light above the tank and tried to wave with towel, another man worked with towel too, and camera man had to wait the right moment to shoot. It wasn't easy! 100+ shots total and only 3-4 which are not bad.