Bullet-proof set-up procedure: introduction of CUC and fish

Snails first for four weeks, then fish: bullet-proof set-up.
There's this notion that's gotten started that the goal line for finishing the cycle is to drop a fish in.

I recommend you get your fish, yes, but put him in a quarantine tank.
At the same time, get a handful of micro hermits (scarlets are my favorite) and appropriate snails and put THEM into your main tank. And get your refugium (fuge) going if you're going to set one up.

Have your lights and skimmer and everything running. You should start to see some green in that tank soon. If you don't, start feeding a little flake or pellet for the snails.

What's going on? the bacteria that started their march to tank conquest are still going, colonizing the INSIDE of the rock, where there are pores you would need a magnifying glass to see. The rock and the sandbed are giving off a little (we hope) phosphate, which is starting to fertilize the algae spores that are in your water (likely)---so algaes will turn up, greening the rocks. WHich the crabs and snails will eat. They will poo into the sandbed, where bacteria will digest that very vegetarian poo, and grow and multiply, in layers very like a torte (14-layer) cake...one kind up top, and different kinds at different levels. As your tank matures, (not this early) you'll be seeing bubbles of nitrogen gas begin to rise occasionally, which is the last gasp of a bit of nastiness on its way to exit.

By the time your fish exits quarantine, to make a smooth transition, the sandbed will be ready for him. Now that that qt tank is empty, go fish-shopping. You could also add a coral IF you have the right lighting and the right tests and supplements. That's another post. 4 weeks in qt, then add the fish. Every 4 weeks (giving the sandbed and rock in every instance time to build strength for the next addition) add another fish until you have them all.

If you do this, you should have a goof-proof smooth entry into the hobby with very little prospect of trouble.