THE VERY VERY VERY ULTIMATELY SHORT WAY TO SET UP
Buy a tank suitable for what you want to keep. These aren't guppies. And corals do grow, pretty fast. Smaller than 50 gallons is much harder than larger than 50 gallons. A sump is next to essential for a reef and a good idea for any tank. Buy a quarantine tank. A pump. Lights (research here). A skimmer. Heater. ATO (autotopoff.) A reef-ready or 'drilled' tank is ready-to-use. Non-drilled means you drill the glass. Lids and canopies are a liability...

1. get a refractometer and figure how to use it. [Not rocket science, but there's a 0 in that 1.025 that is very important...]
2. get tests for alkalinity, calcium, magnesium, and alkalinity buffer as well as your test strips for ammonia/nitrate. Get a little notebook, and start logging your tests.
3. turn on all your equipment and get the temperature as close to 80 round the clock as you can with everything running, including your lights.
4. read the stickies in New to the...

Tank crash: when your chemistry goes south, your fish and corals die, and your tank ends up a toxic soup.

Warning signs: ANY of these warrant a fast series of tests and remedial action: tucked in corals, fish up at the top gasping, or all hiding, green water, mucky brown water, test results off the edge, high temperature, as in, 84 and upward.

Actions to take and why: 1. relieve the bioload. Fill your qt with new saltwater. Use a mixing pump to accelerate the mix, or...

Disease for beginners...
There are 4 sorts of ailments that befall fishes.

1. germs. Bacteria. These are single-cell organisms about the size of a single blood cell that get into a fish and spread very fast by dividing. They are treatable with ANTIBIOTICS. There IS a slight catch in this: bacteria come in two varieties, one called 'gram positive' and one called 'gram negative', for reasons of how they show up when stained fro a microscope slide. When you treat, you have to...

How a CUC REALLY works...and it's probably not what you think.
A Cleanup Crew [CUC] is the next step after cycling. There's a lot of myth, a lot of angst about hair algae and 'getting something to eat it.' Fageddaboutit...re the 'eating' thing.

Your CUC will eat algae. So will copepods and many desirable creatures in your tank.

But they won't strip your tank of algae. They can't. Not remotely. Algae grows because your rock and sand have some phosphate (algae...