If the aquarium is large, I would recommended getting some Japanese goldfish. There is a restaurant in town that has some in a large tank and I just love them. My son also loves them. They are large and colorful enough to actually draw attention and be entertaining. For saltwater I'd get something like:
*Clownfish
*Damselfish
*Lionfish
*Butterflyfish
Please research these fish, because some you can not combine.

Personally, I like saltwater fish the best, but they are so hard to maintain. If she will have someone to maintain the tank for her, then maybe she could consider the saltwater fish.

At my doctor's office, the tank is 1/2 terrain and 1/2 water. There are two turtles in the tank. It's really fun to watch them swim. They aren't very colorful, but they do give the eye something different to look at.

The type of fish that you get for the office will largely depend on the type of tank that you are going to set up. A saltwater tank will allow you to have the most colorful fish, like clownfish or platys, but these tanks do require quite a bit of maintenance. If you do not take care to maintain a proper environment in the tank, then the fish are likely to die very quickly. Therefore, it may be preferable to get a freshwater tank, which still requires maintenance but does not have as delicate a balance. For a freshwater tank, cichlids are a good bet. These fish are hearty and adaptable as far as fish go, and are likely to survive even if the tank is not perfectly maintained. Make sure that you do not overpopulate the tank though, as cichlids will get territorial and fight if there is not enough space.

I have not seen an office aquarium, but I have seen them in the dentist's office and also at the veterinarian's office. At the veterinarian, they chose a wide variety of fresh-water fish. At the dentist's office, it is a salt-water aquarium full of beautiful and exotic tropical fish, and the habitat is a miniature living coral reef.

I understand that the salt-water aquariums are expensive and a lot of work to maintain. I also know friends who have them in their homes and home or office, they all have guys who come in to maintain them. Sort of like a pool man, only different. Therefore, I'm going to assume we're talking about a fresh-water set up.

If your friend and/or his mom will be taking care of the fish tank, they will want some hearty fish, I would imagine. I found a great site with recommendations for the top 10 fish for new aquarium owners. Black Tetras are at the top of the list for "breaking in" a new aquarium and are described as "hearty." If your friends don't want to hassle with a heated aquarium, the suggestion is Goldfish. Perhaps a good variety of goldfish would be nice for starters, and easy to care for. I know there are a lot of really cool looking fish that fall under the goldfish species, especially the bug-eye black ones. That's my opinion, of course.