Melissa
Hi, welcome to the board and the marine hobby. As you can see there's lots of advice to be had.
From Bobothewizard,
I especially wouldnt really worry about the crabs/clean up crew, as they will not add to your bio load on your tank unless you try to stick a few hunderd crabs in there
I would like to clarify something in the above quote, every living thing you ad to your aquarium adds to the bio-load, including the very bacteria that makes the nitrogin cycle happen. All living creatures eat something and that produces waste and that is where the term bio-load comes into play. If a fish dies and left unattended too or uneaten food is left to rot that leads to an increase in bio-load.
Putting to many creatures to fast into your aq is the most often committed error of newbies.
Slow down! Enjoy the view! If your LFS has something you can't live without, relax there'll be another one.
The most important obligation we have as reef/fish hobbiests is to provide the safest, most comfortable environment possible for our charges. If we fail to learn to do that, then we are guilty of consumption. Learn to keep them alive for extended periods of time (years). You will enjoy them much better that way.
Did you add to many? It kind of sounds like it to me. But what is done is done. Now keep them healthy and alive. They will reward you with many happy moments.
I know because I have been this hobby for 55 years.
Happy Holidays
The Oldest Salt