A Guide to Breathtaking Aquarium Photography (+ Tips)
Briefly

In low-light scenarios, your camera will automatically slow down your shutter speed, which will amplify camera shake and fail to freeze subject movement.
Choose a shooting mode that lets you dial in the shutter speed directly - either Shutter Priority mode or Manual mode.
If you set your camera to Shutter Priority, I recommend setting the ISO as high as you can without risking image-ruining noise.
Shutter Priority mode lets you select the shutter speed and the ISO, while the camera automatically picks the aperture.
Read at Digital Photography School
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