Here is the list of what you need to start a SW tank.
#1-Dry Rock, there are a few hitchhikers on Live Rock that people want to stay away from, so they opt for using Dry Rock, or Dead Rock. Macro Rock is a good place to start looking for that. Either way you go you will need a minimum of 1lb per gallon.
#2-Replacement filter media like filter floss and activated carbon (if you get a filter) Which is really not necessary.
#3-Multiple Power heads (2 or 3) 10x your water volume for just a Fish Only With Live Rock, and at least 20x your water volume for a Reef Tank. So lets say your going reef, and you have a 100g tank, you would need flow in that tank at minimum of 2000gph, or 2 1000gph power heads.
#4-Protein Skimmer, rated at 2 times your water volume. Unless your tank is under 30g, in which case you can do 10% water changes a week to rid the system of detrius. But, you'll have to watch the water parameters close, if things go haywire, you'll have to do more water changes.
#5-Saltwater Test Kits. Reef Test Kit. Test for Ammonia, Nitrites, Nitrates, PH, Phosphates, Calcium, ALK and Magnesium.
#6-Saltwater fish food. Mysis Shrimp, Squid, Cyclopease, Algae Sheets, Romaine . Flake food is not really a good food to feed your marine fish.
#7-Aquarium vacuum. This one is iffy. Most don't use one, if you have enough flow in the tank you won’t need one
#8-Rubber kitchen gloves
#10-Two, clean, never used before, 5-gallon buckets
#11-Aquarium thermometer, digital being the best
.#12-Brush with plastic bristles (old tooth brush) - needed for cleaning the live rock if you don't get Fully Cured Live Rock
.#13-Power Strip, possibly GFCI outlets by the tank.
#14-Optional but definitely recommend getting a Reverse Osmosis or RO/Deionization filter for the make-up water, and a barrel for storing the water.
#15-Possibly a Quarantine Tank for your new fish. They sit in here for a few weeks to kill off parasites and bacteria, to keep it from getting in your main tank
#16-Heater rated for your size tank.
#17-Saltwater Mix. Marine Salt. Instant Ocean is the cheap Salt that beginners and Advanced use alike.
#18-Saltwater Hydrometer or even better a Refractometer, which is more accurate. There is also a Digital Meter that is way advanced if you have the cash.
#19-Aquarium filter (not absolutely necessary if running with adequate amounts of live rock, but nice to have if you need to use a mechanical filter or activated carbon, or GFO and such)
#20-Aquarium substrate such as live sand or crushed coral. Some go bare Bottom, others choose the 2-3" bottom, others, more advanced will try the Deep Sand Bed, which is over 6" deep.
Blennies: Blenny Fish Species Including Bicolor, Striped and other Blennies
Clownfish for Sale: Clownfish Species for the Home Aquarium
Gobies for Sale: Goby Fish Species Including Shrimp Gobies
Chromis for Sale: Blue and Green Chromis and other Reef Species
Beginner Invertebrates: Invertebrates Suitable for Beginners in Saltwater Aquariums
Saltwater Crabs: Hermit Crab Species for Saltwater Tanks
Aquarium Snails: Sea Snail Species and Aquatic Saltwater Snails
Sea Urchins: Live Red, Black and Pencil Sea Urchin Species
Aquarium Shrimp: Cleaner Shrimp Pistol and Coral Banded Shrimp