I just wanted to 'somewhat' elaborate on the topic, so I decided to write an article. This is a somewhat controversial subject among hobbyists everywhere, and the following is just what I would do.

LIGHTING :

Lighting will depend on what you are planning on keeping in the tank. It is also a key factor in ANY marine tank containing any pretty much ANY photosynthetic coral. Not many corals can not survive with the normal output florescent bulbs that come with tanks. What we are doing with our tanks is trying to mimic their natural environment as closely as possible. So to close this section I would recommend figuring out what type of corals you want to keep, then posting a thread in the proper forum here with the info in it. This will make it a lot easier for the community to help you. You should NOT try to save a few bucks when purchasing.

PROTEIN SKIMMER :

In my opinion, a protein skimmer is a VERY important piece of reefing equipment. What it does is remove excess waste and nutrients from the water, leaving you a better environment for your livestock. They also add oxygen to the water, it may be a small amout, but every little bit helps. This is another piece of equipment that you should NOT try to save a few bucks on when purchasing.

POWERHEAD PUMPS :

When looking into powerheads, it is again, a good idea to have a list of corals, fish, and inverts that you are planning on keeping. We use powerheads in our tanks for water circulation that does not count as part of the turnover rate of the system. There are a lot of options in this department that are available to us.

LIVE ROCK AND LIVE SAND :

Live Rock is going to do the majority of the filtration in a marine tank. To save a few bucks, you can also buy "base rock" or "dead rock" from most LFSs that sell live rock. I recommend Marco Rocks The finest aquarium rock available, base rock, live rock, reef rock, marco rock, reef tank saltwater fish, live corals, Marco rocks, Fiji live rock, Tonga Live rock, then buy a couple of pieces of live rock to "seed" the base rock. Base rock is pretty much just dead live rock.

Sand is used for many reasons in a marine tank. the main reason, IMO, is for nitrate reduction within the system.

TEST KITS :

Test kits are a very important part of owning a marine tank. We rely on them to let us know what our water parameters are and what needs to be adjusted within the system. I highly recommend these being in the first round of purchases made for setting up a tank, and that you always have them available to you.

RO/DI SOURCE :

RO/DI water is what is suggested to use in our tanks. RO/DI is a filtered water that has pretty much every chemical that is in it removed through a series of filters, the result is pretty much pure water. There are many options for getting RO/DI water. You can either buy a unit for your own personal supply, or you can get it from most LFSs that sell marine equipment. The LFSs usually sell it pure or premixed with salt, at a usually lower specific gravity. If you buy from the LFS at first ... I recommend testing the water before adding it to your tank.

This is a list of equipment that is usually recommended when setting up a new marine aquarium. It is in no way a "you HAVE to have this" article on how to set up a marine system, but a guide line for all new comers to this wonderful hobby. I hope it helps you to understand some of the equipment that we use and why we use them.