Taking photos in an aquarium can be challenging at best. On one hand, the lighting is really beautiful and striking - what with the blue glow and all - but on the other hand, things are prone to be too blurry, dark, and unrecognizable if you don't take the right steps. Lilangelfish e-mailed me asking for some quick tips for her upcoming trip to an aquarium and I thought you might all be interested in what I learned.
The first issue with aquarium photos is that you are usually shooting photos through glass, and if it isn't clean, the spots will show up in your photos. Also, spots on the glass will throw off the auto focus mechanism of many AF cameras. Problem number two is you're shooting through water, which bends light in funky ways. To deal with this, all photos should be taken with the lens directly perpendicular to the side of the tank. If you shoot at an angle, the view will become distorted and your fish will look either elongated or compress. Third problem is that you are shooting moving targets, which means it's hard to get a focus lock on them. For solutions to these problems, just read more
Shooting moving objects
You can change the aperture of your lens to the smallest setting you can get away with (this takes some experimentation) to increase the depth of field. Another solution is to manually prefocus the lens to a point inside the aquarium and wait until a fish swims into that plane of focus. Both of the above will only work on those cameras that allow you to change those settings. Most point-and-shoot cameras will not allow you to change either setting, and will not be a good camera in general because of the flash issues.
Use the right camera
If possible, do not use a built-in or on-camera flash. The best thing to use is an off-camera flash.
Work with your flash - avoid it if you can
If you must use the built-in flash, or a flash that sits on the camera (almost all point-and-shoot and SLRs), you may have a problem of the flash reflecting off the front glass and into your lens, ruining all photos. Option 1: Turn off the flash if you can, or put some black gaffer tape across the flash if you can't turn it off. This means that the flash won't illuminate the tank. Problem is, this might bring you back to the lighting issue. Option 2: most cameras today use something called TTL (through-the-lens) technology to shut off the flash output when it reaches the proper level for exposure. Problem is that the flash reflecting off the back of the tank will influence TTL and you will not get good illumination of the subject you are shooting.