This might be better in the general discussion area. You would get more feedback from a wider population. I am not sure you need to be an Expert to keep SPS without a reactor
You also might want to specify some things.
What is long term?
Any particular species?
Other specifics about set up, etc.
I have sucessfully kept every SPS I ever had without a calcium reactor until I got bored with dosing B-Ionic. There is no secret or trick. Just patience and diligence. I even kept them without an RO/Di for 5 years (Problems included hair algae and high phospahte levels amoung other thing) sucessfully.
Deep sand beds, Plenums and all of those other things that people complain about with facts and stories of woe are crap. It all comes down to husbandry,and stability.
All of the new devices that we use now are just to keep things easier (does not always work out that way) and a more efficient way to keep CORALS , not just SPS.
People have to figure out the best way to do that for themselves.