Coralline: what good is it, what harm is it, and do I want it? Informational.
Coralline is the purple-violet stuff on your rocks.
The bennies of having it on all your rock: a good coralline coating principally means other, more objectionable algae can't grow there efficiently. It probably (my guess) does limit efficiency of water reaching inside your rock, but if you have holey rock, you have plenty of exposure, including the part sitting on the sand, where this stuff won't grow....

Do I need GFO? What can it do? Informational.
GFO is granulated ferric oxide. Iron, in other words, in a particular form.

It can be added in a bag for a very small tank, BUT---to really be effective, you need a GFO reactor. These, fortunately, are comparatively cheap, and require only a small pump to run. They also come in more than one size.

Here's what they do:

A GFO reactor sucks up phosphate, which you do not want in your tank---because it...

Critical decisions: Important to understand what the Issue is:
1. Acclimation: is almost totally about salinity. Equalizing the temperature can be done with a 15 minute float of the still-sealed bag under most circumstances. That is less critical than a salinity match.
a. It is safer to jump DOWN in salinity than up.
b. It is not safe to raise salinity more than .002 at a go.

2. cycling: is all about ammonia. Which is what you DON'T want. Clean water is ALWAYS...

CYANO: how to fix it.
Cyanobacteria AKA cyano is not an algae. It's a bacterial sheet. It's red or brown (according to your lighting) and it has oxygen bubbles in it. This stuff is ancient and ubiquitous (everywhere). It gave Earth its oxygen after the Permian Extinction (before the rock that got the dinos). It is the foundation of the photosynthesis of all green plants.

So forget trying to avoid it. It's probably in every house and pond on the planet.

Every...

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...