Question
I HAVE A SMALL POND WITH 3 GOLDFISH.  IT ALWAYS BECOMES GREEN AND DIRTY LOOKING.  HOW CAN I KEEP IT CLEAR?  I HAVE THE PUMP AND FILTER THAT CAME WITH THE POND.

Answer
Seems like you are having algae problems. A regular filter does not always help with algae issues.

I use 2 things to fight algae in my pond. One that I think works great is Barley (a natural way to fight algae and dirty water), as barley ages in your water for 2-4 weeks it will create a "good" bacteria that will kill and prevent "bad" bacteria and algae.

Also add some plants to your pond if you have not. Plants will rob the algae of nutrients that algae needs to survive.

Another thing I use is a UV light. The UV light will promote clear water and kill microbes and algae. Search for a UV pond filter on google.

Too much direct sun will cause problems like you describe. Try shading your pond as needed.

I hope this helps some.

Here is a good article on algae:
http://www.koipondmagazine.com/the-control-of-algae-a4.html