About skimmers: y/n/maybe? FYI And they aren't your swimming pool skimmer...
A skimmer produces skimmate, a brownish watery to dark murky yuck that otherwise is dissolved in your water. It does this by frothing the water, and the more efficient skimmers churn the water into a foam that would stand like meringue in a cup. Do you want this stuff gone? Well, lps and soft coral will consume a bit of it. But unless you have a packed reef, their usage can't compete with a skimmer. And, catch-22,...

There was a time the earth was pretty much rock and water.
Somewhere, probably around volcanic deep sea vents, in the pores of the rocks, life got started, chains of amino acids, dna, rna, etc---and we got, yes, slime.
We got algae.
We got cyanobacteria which happily took up carbon and water and spat out oxygen after absorbing energy from the sun (photosynthesis)---this was a bad thing for things that didn't like oxygen, but it was good for, well, everybody who wasn't a microbe...

Slime coats and you...yes, they matter.
Fish have an insulation, a slime/moisture that coats their bodies and protects them from both iffy water acidity and chance encounters with parasites; it also may limit bleeding in injury and promote healing of minor scrapes.

Things that diminish the slime coat: the alkalinity of your water being out of bounds (the range should be 7.9-9.0 on the dkh scale, and if you aren't testing your alkalinity weekly, you should be. Daily, when just...

Do NOT buy coral while your tank is still having problems like massive algae, excessive cyano (most tanks get a little now and again).

Do not buy corals until you have 1) proper lighting 2) test kits to be sure your water is ok. And supplements to KEEP your water ok. 3) dips and in the case of softies (and stonies you don't trust) an observation tank with proper lighting.

First, the lighting. If you do not have light it hurts your eyes to look toward, no sps (colored...

Everybody has certain unwanted species arrive. NOT everybody has them take off and become a pita.
An exception is caulerpa algae in your rockwork: THAT is a plague that can cost you all your rockwork if your tank is too small to accommodate one of the only species that will eat it (rabbit).

Hair algae is a piffle. Most everybody gets it. A tank that continues to have it past a few weeks has a lot of phosphate it shouldn't have. Instead of buying a critter alleged to eat it---get...