You need to be in the right area, with the right knowledge to suceeed, most of the people that have got this are already doing it.
gotta have that knowledge and years of experience there.
Service isnt really a unique selling point in this market anyways as its really a service orientated industry - poor servie/advice people will soon get fed up and go elsewhere. Offering the level of service expected or above and beyond will help to attract a loyal customer base, which is essential to succeed.
If you could start a shop with its own coral prop sytem so as not to damange the natural reef, then this could work as a USP. But companies like reefworks and fishmanfrags are already there. It would also wach costs up massively
Like i said, its not impossible, you just have to make sure that every aspect has been thought about.