Sounds like you got out while you still could. I've seen lots of red flags here. The nurse and yourself should have been no where near this aquarium. This is a lawsuit waiting to happen. Hospitals almost exclusively rent aquariums so that the maintenance company carries the high insurance policy. Everything in a hospital is astronomical in price, the damage from a 120 gallons of water like that could shut it down for quite a while, requiring new flooring and drywall work at best. Shorting out power and causing power surges to equipment can be millions.
As for bacteria from an aquarium, sure the odds are low. However a business has virtually nothing to gain by providing an aquarium and will see it as a liability. I run a store with aquariums, no matter what we do, virtually you always have the public putting their hands in water. You can detour it as much as you want, but nothing will really stop a kid or an adult from getting into the water. Short of physically stopping someone. Which isn't allowed either due to lawsuits.
Steps can be taken to mitigate risks, such as building the aquarium into the wall with access only through a locked door. Having a 3rd party carry the insurance policy etc. Using thick acrylic instead of glass and other factors.
Aquariums are beneficial, however they are also a liability. It's up to a business to evaluate the risks and do what they think is right to mitigate it. It seems especially unfair after being in place for so long, but people are just doing their jobs. I found it best to focus my efforts away from things like hospitals and more into co-op schools and schools in general. With co-op schools being the most open to an honest aquarium in the class room for kids to be a part of.
I'll commend you if you change their mind, but in my experience the more it's fought the more they just dig in against it and maybe even pass policy that is even more restrictive. I've seen that happen in schools.