Many pool owners experience algae at some point or another and that's ok.  The challenge with algae is, you have to catch it before it gets out of control.  Once algae has been observed you just need to act and not wait thinking it will go away on it's own or it will not get worse without doing anything, because it won't!  But. don't panic!  You just need to follow a few easy steps:  FIrst, you need to shock the pool.  Most times once you have algae, the liquid is not enough.  You will need to use powdered shock.  I useTrichloro-S-triazine (trichlor) or dichloro-S-triazinetrione (or dichlor).  Dichlor dissolves a lot faster and so most  people prefer it to trichlor.  Secondly, you need a good algaecide.  I use Algae Control made by PoolPals most times.  This is an inexpensive, non-copper-based algaecide that works well when used in conjunction with the powdered shocks.  After adding these two chemicals to the water, I usually give the pool at least a day to circulate and for the chemicals to take effect.  At this point, I use a stainless steel algae brush to brush away any remaining algae.  Most times, the algae will brush off with a minimal effort.