Try using flash. Your camera will register a quicker shutter time and will catch the fish easier. Don't use your phone/camera parallel with the tank but angle it up or down (down is easiest) to avoid getting the flash glare. Also, wipe down the front of your tank with some window cleaner so you don't get a bunch of streaks haha, I always forget to do that part. And don't worry, flash doesn't harm the fish.
Wilds: Wajok, Rutilans, Siamentorialis, Hendra
Leopards: Luna, Astrael, Dorian, Cullen, Gallifrey
African Fat Tails: Nox and Lux
Bearded Dragon: Stormfly