Because they are living creatures, corals have some compatibility and habitat considerations too. Here are a few factors you may want to make a note of during the planning phase of your saltwater / reef tank:
Compatibility - Check the compatibility of the corals you wish to use, both with one other and with the fish you intend introducing. For example, if part of your plan is to introduce anemone to give safe haven to your clownfish, do bear in mind that anemone eat certain other species of fish as well as shrimps.
Space - Offer each coral sufficient space within which to thrive. Like any other sea creature, coral will become aggressive if competition is perceived. When introducing soft coral, leave a clear space of approximately 3" around it. Hard coral, on the other hand, will require at least 6" of clear space around it.
Tip over potential - use epoxy to keep unattached coral in place when you first introduce these, otherwise it may tip over onto a neighboring coral, burn and die.
Lighting - this plays an important part in photosynthesis. Different corals have different lighting requirements which should be thoroughly researched. To achieve optimum beauty, it is better to select corals with compatible lighting needs.
Current - corals rely on the water movement around them to help keep them clean. Also bear in mind that different corals have different current requirements. Powerheads or a similar source of water movement should be installed to create current.
These factors, together with placement, will be the difference between success and failure.