A friend of mine owns a restaurant and they had a 72 gallon saltwater aquarium that was brought in and set up by the same company who services it. When a fish died, they replaced it, or they would change fish for different fish. I think it became a health code issue thing for him and he had to have it removed. Same with my friend who had a tank in their bar.
Now, if your company was the one who provided the aquarium, equipment, decor, and livestock to these doctors/dentists offices (etc) and could sell them on the idea of having one in their lobby, then you might be able to get a business rolling. You provide everything to create the aquatic scene in their lobby and they pay you to take care of it. That sort of thing might go hand in hand with a custom aquarium making company too.
Definitely networking with other companies would be a good way to help you get started, at the very least you’d get practice using your “1 minute pitch” to sell yourself. Don’t think that other companies are going to work as hard at getting business for you as you would though. If you’re lucky you could get them to mention your service on their website or perhaps even provide a link to your website (that also helps with search engine optimization on your own website). So you would have to market for yourself too.
How are you going to target those particular business owners? How many potential business owners do you have in your area? What size will be your serviceable area? Are you going to create a flyer or brochure, print up some business cards, then go in and start talking to receptionists, asking them to share this info with their office’s decision maker? Are you going to create a website so local people can find you and hire you?
How many businesses in your area already have aquariums and use an aquarium cleaning service? Is that a need in your area? You need to do a market survey.
You could also ask those businesses who already have a large aquarium in their lobby if they are happy with their aquarium cleaning service. Ask them if they could tell you the name of the company they use (if any). Then take note of what they tell you. You may find out if one company has the market in your area already cornered.
I hope some of this info will be helpful.