I started with a 7 gallon reef tank I did put one little blue damsel in because of flatworms but then that turned into a 24 gallon tank for the one fish. My 2.5 gallon reef with snail turned into a 24 gallon then later to a 28 gallon and I have a 40 gallon corner tank and a 55 gallon tank.
Those of us that start small just keep upgrading and getting more tanks until we get what we want.
I have only one fish in the 24, 28 and the corner tank the corner is about a 45 gallon and I could in theory put all 3 fish in it but the lemonpeel would stress the damsel and the midas out.