agreed on the 6' tank. you can really expand your horizons by doing that.
Here are some basic guidlines that are helpfull but not always 100% acurate, just something to start on.
1.) you want at least 1-2 lbs of live rock per gallon of water in your tank.
2.) If you want to go crazy with your corals you will need a fair amount of light. The general rule is 3-5 watts per gallon, some hard corals and thing require more than that and a few corals dont require any light at all because they don't take from the sun, they take from the water instead. Also the watts per gallon isnt allways accurate becasue different types of lights put out more sunny goodness than other types. The t-5's and metal halides are very popular.
3.) get some good flow in your tank with powerheads or some sort of water movement
4.) alot of people go with a sump/refugium, which is anotehr area to house water that usually goes below the tank and the water out of your tank flows by gravity down to the partitioned tank below that generally has more item in it that help naurally filter out thing you don't want like phosphates and nitrates and add things you do want like oxygen. you can put more live rock in here with some more live sand or mud as well as some plants that absorb bad and give off good, just like trees outside. then you have a pump in the final chamber that brings this water back up to your dispaly tank.
5.) protien skimmers are also very popular as they are fairly inexpensive and can do alot for your tank in teh way of getting rid of gunk and some nasties you don't want
6.) get allt he test kits you can. the basics are ammonia, nitrites and nitrates, alkalinity and PH, but you can also get them for calcium, phosphates copper and iodine and even more if you are doing a nice reef setup. corals can be very touchy about thier water conditions.
7.) when setting up a new tank you have to go through whats called a cycle
this means that the first water you make up fro the tank won't have much in the way of bacteria, bacteria eats ammonia and ammonia will come from you live rocks and sand so it takes a bit for that bacteria to grow enought to consume your ammonia, and when they do they turn it to nitrites and tehn into nitrites and alstly into nitrogen which leaves your tank and dissipates into the air. This cycle is maybe the hardest part because it can take a few weeks to a few months for this to take palce and its hell waiting to stock your investment full of corals and fish. But you can't rush this part if you want it to be really good, jsut let mother nature take its course and you'll have a fine set up afterwards.
8.) you will definatley want an RO/DI filter system. Reverse osmosis. this is pure water for your top off from evaporation and for freshwater to mix your salt with to make saltwater.
9.) make sure you get your livestock from someplace that is reputable for taking care of their stuff. you don't want to buy a fish or rock that has a bunch or nasty stuff on them that may never leave your tank. Specialty fish stores if you have them in your area are usually pretty good because they know what they are doing when it comes to fish (Usually)
10.) dont forget to make drip loops in your electrical wiring so if you get a leak of some sort it doesnt run down your wiring and into the socket and fry your whole hobby.
Good luck hope this helps for starters.
