If you want to know someone that does/did it on a large (and very successful) scale, check out this video:
https://www.youtube.com/watch?v=Z5RaN76b0Fg His name is Dick Perrin and he owned (owns?) Tropicorium in Romulus, Michigan.
I first started going there around 1992-93 when he went big in his greenhouses. I don't know about him now, but in the mid nineties he was one of the most sought out speakers at Macna etc. and was one of the pioneers of propagating corals. I used to take my reef club down there often. In 1994 I flew in Julian Sprung for a long weekend for a presentation for our club and he really wanted to go there as well, so we took him for a private tour for most of a day and he was very impressed.
As of about 15 years ago, (the last time I was there) I think he was still using home made air lifts as "pumps" for recirculation, large plastic lined wooden "vats" (for lack of a better word) that were around a foot deep, gravel bottoms, a lot of carbon to keep the water clear and supplemental halide lighting, and lots of fish. He also had most of (if not all) of the water running through a large "Rainbow Lifegard" filter system. As I remember at the time there was not a ton of protein skimming going on (but It's been a long time so I might and probably am wrong). It was THE most simple set up imaginable for me anyways. And I am sure he had way to heat everything properly also.
When I googled him for this post I noticed his web address was gone. I was just on there a few months ago and it was up and fine. He still has a Facebook account but I didn't take a look at it. I do know that he got very busted in Florida for illegal wildlife trafficking.
https://www.justice.gov/usao-sdfl/p...lead-guilty-illegal-trafficking-marine-life-0 but I have no idea whats going on now.
Anyway, off subject I know but it would be a great place to visit if your thinking about doing it with about as little start up cost as I can think of. Having been there myself, it definitely would be the place that I would want to see in person if possible. It's in the same general area as the Detroit Metro airport and easy to get to. Either way there are quite a few youtube videos to check out if you want.
Good luck on your future endeavors no matter what they be! And message me if I can answer anymore questions.
Thom