Eek return the domino damsel immediately if its not on your eventually wanted stock list. Not only is it better to do fishless cycling, dominos are some of the most aggressive of the damsels and will harass and possibly kill any other fish you add after.
Take my advice as a newbie in the saltwater community as well.. please buy a QT tank - you can get a cheap 10 gal
set up for about $30 ( filter, light, etc). I made the mistake of buying non qt clowns from a lfs
here, put them in my tank, they had ich, and showed signs within a few days, one died, and both contaminated my aquarium - couldnt keep fish in the main display for 7 weeks. You'll save yourself some headaches and save your fish if you get a qt. I'm just now putting my first clown inthe main after 7 weeks.. frustrating!
btw, you'll save yourself a lot of money if you buy a large 5 gal
container of salt mix and mix it yourself. a $30 ( roughly) bucket makes about 160 gals at 1.021 sp gr. Ive seen 2 gals of the premixed water go for about $10-15 on the shelf and about $1 a gal
from the lfs
- but I wouldnt trust the water if you cant trust their advice. Its really easy to mix most salts too, as long as you follow the directions.. which are pretty streight forward. I personally use reef crystals.
Anyway, welcome to the hobby and feel free to ask q's here before buying anything / talking to your lfs