I find shooting at aquariums to be a challenge. I was at the Monterey Bay Aquarium a couple of weeks ago, so I'll tell you what I've found.
Some general tips:
1) Wear dark clothing. You will be shooting through glass. You want to minimize reflections.
2) If you have a hood, press it directly against the glass. That will totally eliminate reflections. You can get a similar effect, but putting the lens really close to the glass and using your hand to block some reflections.
3) Glass can do funky things. The thicker the glass, the funkier. Scratches can also be an issue. The bigger your angle to the glass, the more it will mess up your pictures. Shooting straight through is prefer if you aren't using a flash.
4) You can use a flash, but you have to be careful. You want to angle it so that the reflections don't bounce back at you. Even then, it will light up any smudges or scratches on either side of the glass.
5) Don't bring a tripod or monopod. The would be useful, but the MBA doesn't allow them.
The jellies (fka jellyfish) are easy to shoot. The light is pretty low, but it is really nice. Definitely DON'T use a flash here. You'll ruin the effect.
This shot was taken at 24mm on an APS-C camera. It was taken at ISO 1250, f/2.5, and 1/60. Your lens won't get down to f/2.5, but it will do f/3.5, which is one stop away. So if you shoot at ISO 1250, you can get the same shot at f/3.5 and 1/30s, which should be fast enough. Don't sweat the details. With your camera, you can just go on auto, point, and shoot.
Here is a similar shot. Same gear. f/3.2, ISO 800, 1/60
There is a big, dark room with a reasonably lit aquarium. It makes for a nice silhouette shot of your group. This is a pretty low light shot. I was at 24mm, f/2, ISO 1600, and 1/30. Your lens will be about two stops slower, so you'll need to either boost the ISO to 6400, drop the shutter speed to 1/8, or split the difference at ISO 3200 and 1/15.
Don't miss the super funky sea horses. This shot is at 24mm, f/2, 1/320, and ISO 800. You should be fine with this. Your camera will probably pick something like f/3.5, 1/80 and ISO 800, which should work OK.
A lot of the tanks are well lit and don't require a flash, super gear, or heroic techniques. This shot is 24mm, f/5.6, ISO 1600, 1/500. In general, I would recommend erring on the side of higher ISO than you normally would. Those little buggers don't stay very still, so you need a relatively quick shutter speed.
This shot was at 105mm, f/4, ISO 12800, and 1/125. That tank isn't very bright, so you might try a mix of flash and no flash. Remember to be at an angle when you use the flash and straight on when you don't.
Don't forget to get some shots of the aquarium itself.
Good luck. Have fun.
