1. To help support your hobby spending. This hobby can take quite a bit of money even for a nano tank. By propagating corals and selling or trading them to other hobbyists or pet stores you can help offset some of the money you spend on your tank. 2. To help save the reefs from over collection. While this topic is somewhat controversial (some say the hobby does very little damage compared to other outside factors such as farming fertilizer runoff, dredging, tourism, etc… while others say the hobby is responsible for lots of damage) it is nice to be able to minimize any damage to reefs in the wild. 3. For healthier specimens. Tank raised/propagated corals generally are much hardier than any coral taken from the wild. These propagated corals have already adapted to artificial light and generally do not have to deal with shipping stress (if dealing with local hobbyists).
4. Help sustain the hobby for years to come. Some studies have shown many reefs may die over the next 50 years due to global warming, the rising temperatures of the oceans and ocean acidification. If these reports hold true the corals we are propagating and keeping in our tanks may someday be the only corals left. By propagating corals we will be able sustain the hobby along with the possiblity one day reseeding the oceans with corals. 5. For education purposes. There have been numerous schools across the country that have started to include coral propagation in their science classes. This is a great way to help kids and adults learn and become educated about corals, aquariums and even the plight of coral reefs in our oceans. 6. For the health of your reef tanks. Corals in our aquariums are in a constant battle with each other for space. If corals are left to grow unchecked in the tank, the ones that both grow the fastest and shade out their competitors or the ones with the most powerful sting can eventually take over the tank killing off the other corals. By pruning back and propagating the corals you help to prevent this from occurring.
7. Making new friends by trading. Throughout the US and the rest of the world there are aquariums clubs where people with similar interests in reef aquariums meet to chat, learn, trade and make new friends. 8. A good way to get that hard to find or expensive coral for less money. Buying whole colonies of some of the rare corals can be quite expensive and/or very hard to find. But buying a propagated coral you are usually able to find those hard to find corals much easier and those expensive colonies are much more reasonably priced when purchased as a frag. 9. Because it is fun and easy. While not every coral is as easy as others, it can be a lot of fun learning how to propagate corals and watch them grow out. You can even record and keep track of frags you sell or trade to see how they do for everyone. Many of the corals we keep and even certainly anemones can be propagated so why not give it a try. 10. It is for hobbyist of every level. One of the misconceptions of coral propagation is that you have to be an expert reef aquarist to have success. This can’t be further from the truth. Coral propagation can be done by hobbyist of every level, beginners to the advanced. With the help of books such as Anthony’s Calfo’s Book of Coral Propagation and fellow hobbyist anyone can propagate corals.

i found the link here but it is a slow loader so i just pasted it here

Rock

http://kb.marinedepot.com:80/article.aspx?id=10623&utm_source=mdnl20080418&utm_medium=mdemail&utm_term=mdnl20080418top10fragyourcoralslink&utm_content=mdnltop10fragyourcoralslinkrock.ccct@gmail.com&utm_campaign=mdnl&fromsource=mdnl20080418top10fragyourcoralslink