The best thing to do is decide what you want to grow in the tank. The types (if any) of coral will dictate the lighting and flow needed in the tank. After that there is a pretty simple way to do the rest; Live Rock, a good skimmer and temp control.
The live rock will provide
biological filtration needed to help keep the water clean, the side of the filtration equasion is the protien skimmer. Generaly everyone will tell you to get the best you can afford. I can say from experiancce this is great advice. The skimmer removes disolved solids from the water and keeps things from staying in and going toxic on the critters.
Many people use diferent types of filtration methods such as
canister filters, wet dry filters etc... and have great success. Each method has its merits. You will find most prefer the method of rock and skimming. Of course there are different levels to all of these methods and all kinds of extra step and additions that can become much more specialized and accordingly expensive. Live Rock and a skimmer is the basic and affective step to a healthy reef system that many if not most people use. HTH
Robert
