There are many logistics you need to answer first. Have you discussed a compressor with your insurance carrier? Have you researched your Canadian Labor Safety group (OSHA for us in the US) the requirements for employees? Do you know the proper air standards and periodic testing requirements?
I caution you to really understand the filtration systems. As an example, I have a Bauer Oceanus compressor for personal use. The reality is, the factory filtration produces high quality air, but the rated capacity of the filter in real (warm) conditions is abysmal, needing changes frequently (I think I got 8-10 fills, and it is "at capacity" per their published information. Far short of "rated capacity", and filters are an expensive consumable. You may likely would want to upsize filtration (which adds cost).
Single phase vs. 3 phase power? As an aquarium, you likely have 3 phase readily available which is a better option.
I caution you to really understand the filtration systems. As an example, I have a Bauer Oceanus compressor for personal use. The reality is, the factory filtration produces high quality air, but the rated capacity of the filter in real (warm) conditions is abysmal, needing changes frequently (I think I got 8-10 fills, and it is "at capacity" per their published information. Far short of "rated capacity", and filters are an expensive consumable. You may likely would want to upsize filtration (which adds cost).
Single phase vs. 3 phase power? As an aquarium, you likely have 3 phase readily available which is a better option.
With operating a fill station, assuming you have obtained operator certifications, are you needing to have someone versed in tank inspections? You need to know about what you are filling....
I like the idea of a bank for your fills as the compressor (if it can do bank/continuous duty operation) runs much better in the end.
I'd still try to pursue some inter-agency agreement with the FD, especially with both entities under City ownership/control.....