why my live rock have red alge...
any else can xplain to me..

Your rocks have red algae simply because your water quality is terrible. Your aquarium has to mature.

Now, before you start speaking broken english (i.e, xplain), I would like to advise you to take this hobby seriously. Go read a book, do some research, and really engage some experienced hobbyist.

It is very disgusting when Malaysians take marine aquariums lightly. They do not know that coral harvesting is very bad to the environment. Unless you know how to keep them, do not buy them!

So please, go read up on algae. Hopefully, you will learn to use proper english in the process.