Dubai Mall is impressive and seems like a tardis.  It is not complete, but  they have done a very good job of opening a good varied selection of stores throughout, making it well worth a trip.  You can easily do a broad variety of shopping from food and groceries to clothes and accessories.  There is a good selection of restaurants there too,  including Ruby Tuesdays.  The indoor ice arena is open and worth visiting, even if you just want to stop and watch the people skating on your way round.

The indoor aquarium has a viewing tunnel through the middle, a large fish tank measuring about 45 metres and home to some 33000 species.  You cannot help but feel concerned that there are far too many sharks and fish in such a small area.  If you just want to see the aquarium you pay 25aed per adult or 50aed if you want to visit the Discovery Centre upstairs as well. However, though first impressions of the Discovery Centre are pretty good, some nice fish in relatively large aquariums with good educational guides, further round you come to extremely small enclosures housing otters, penguins and seals.

The enclosures for the otters and seals could not be more than 12ft by 10ft housing more than 3 animals in each, which seems far too small.  The mall is impressive enough without the animals, so perhaps concentrate your efforts on the other sites, shops, and attractions the mall has to offer.