I know this is an old thread but I wanted to add my experience ans this thread came up when I searched. I know some of it was covered in this thread already but some of it may not have been. I will be going to an aquarium next week and wanted to practice before hand. A friend of mine has an aquarium so I asked him if I could come over and take some practice shots.
Camera: K-50
Lens’s I tried: 17-50 2.8, 50mm 1.8, 50-150 2.8
Rubber lens hoods: Neewer brand
Some of the things I learned:
1.) Get a rubber lens hoods for the lenses that you want to use, they are cheap on eBay. These will keep light from entering because you can get them right against the tank. I tried both and this made a difference.
2.) Pick a lens that has a fast aperture and can focus close. Once the fish were comfortable with me and the camera they started swimming closer to the glass and my 50mm 1.8 could not focus close enough with hood against the glass. I also didn’t like having the fixed focal length and preferred a zoom. I found that my Tamron 17-50 2.8 worked the best as it focuses close and can zoom when the fish moves. I don’t have a macro lens but it should also work well.
3.)
Keep the lens face at 90 degrees to the glass to prevent glare and CA.
4.) TAv mode worked best for me. I tried Av and Tv and found that TAv was the best because it allowed for ISO numbers outside of the standard (800, 1600, 3200 etc). I kept the aperture at 2.8 and kept my shutter speed on the higher side (above 1/125). If the fish was more active I would bump shutter up to 1/180. If a fish was in a more lit area I would bump up the aperture to get a sharper image. Of course your results may vary but I found it worked for me. With photo editing software and modern cameras being able to handle noise so well don’t be worried to shoot at a higher ISO then you normally would.
5.) When I go to the aquarium I will also bring my 50-150 for any exhibits that are outside and for larger tanks where fish are further away.
6.) White balance is tricky and you really just have to keep an eye on it and adjust accordingly. I also found PP on the more difficult side.