Here's a quick list off the top of my head...If I miss anything which I'm sure I will, I know others will chime in...
Salt mix
Hydrometer
Thermometer
SALTWATER test kit
PH's for water circulation
Substrate
(Old castle sand works great, you can find it at Home depot. I would stay away from
CC with such a small tank as you will probably be battling water quality for a while until you get the hang of it.)
Live rock
(spend the money and load your tank with live rock....you'll be very happy you did 1-1.5 lbs per gallon)
Lighting
(If its a
FOWLR tank...lighting can be pretty minimal...but as with most everyone, I'm sure you will fall in love with something at the
LFS and end up needing more lighting. Try to get 3 watts per gallon anyway.)
Protein Skimmer...
(some people would argue it will take out too many of the trace elements in a small tank...I think its a good idea.)
QT tank
(Maybe you could keep your ten gallon for use as a QT tank.)
1 raw shrimp to cycle the tank. Despite what your
LFS may or may not tell you...don't cycle the tank with a fish. The fish will most likely die. Just use an ordinary shrimp from the grocer...You will find some excellent posts on these boards regarding cycling the tank.
Don't get discouraged by the false claims that
SW tanks are TOO difficult to keep...You'll be fine. Check the reading list on the boards.
Last but certainly not least...PATIENCE...that is the key to having a great
SW tank. Cycle your tank properly, use proper husbandry, and keep up with your maintenance...before you know it, those
FW tanks will be converted...lol....
Good luck...and the general rule of thumb is to keep one pair of clowns per tank.
HTH
Travis