Some corals are easy, and some are very hard....depends on the coral!
Some corals are incredibly easy like mushroom corals, button polyps, yellow polyps. However, there are a couple of things you should know about the above. Some shrimp and crabs will eat the yellow polyps, and mushrooms can spread, some people have a problem with this. Then there are the various button polyps (called zooanthids), they carry the most toxic substance known to man. Here is a thread on reefcentral about this subject.......
http://reefcentral.com/forums/showthread.p...threadid=158663not trying to scare you but to inform you. I have button polyps in my tank and all I do is make sure I wash my hands well after working in it (which you should do anyway!), and I am careful when handling the rock the buttons are on.
The above corals don't require intense lighting and depending on what lights you already have on the tank, you may only need to add another strip light or can rig something up using shop lights with the correct tubes of course.
Other corals in the soft coral family, like leather and toadstool will need more and better lighting like PC's (power compact) or VHO's (very high output). Corals of the LPS family (large polyp stony) like bubble, frogspawn and hammer will need lights like this too.
Hard corals like staghorn also known as SPS corals (small polyp stony) are some of the hardest corals to keep and will need MH's (metal halides). They are also the most demanding with regards to water quality. Clams need MH's too....I know they aren't a coral but threw them in there too since we are talking about MH lights.
Anemones are another story entirely. I will NOT recommend them to any new saltwater hobbyist. They can be very difficult to keep, they need intense lighting (MH) and probably most of all, they need an experienced owner who can find out exactly what they need. Most LFS's will say oh no, they're easy, but they are lying to you. About 75% of anemones die within the first 3 months of being bought. These are animals that can live for hundreds (yes, HUNDREDS of years in the wild) so 3 months is rather dismal.
****getting off soapbox now****All corals and anemones can and will fight one another with stinging cells, tentacles, etc....and also with chemical warfare. It is a good idea to use a skimmer in your tank, and also to run carbon in your filter to help remove these chemicals.
Even though it sounds kinda scary with all the fighting, stinging, toxic, spreading corals, they really are very neat to have.....a real slice of nature in your living room, complete with the struggle for life on the reef.