This area gets a whole page about it because it's such a common problem and there are QUITE A FEW solutions. The pundits will assert that there is only one way to control algae, and, you won't be surprised to discover it's the only way THEY know.
HELP! Sick Fish! Twenty Steps to fish health. You LITERALLY can solve almost any Koi or Pond health outbreak with these twenty diagnostic steps and nothing's hard. But it's not "here's your pill" either. Downloads are available.
DrJohnson.net More than koi health, this site spans all things animal, by a real veterinarian who shoots you straight.
Fishdoc.co.uk By Frank Prince-Iles. A UK authority who put this site together some time ago and which is still relied upon as a major source of good Koi and pond fish information
If you need pet information AND Koi pondfish and pond information you might like DrJohnson.com which has everything from pet info, to vet info, to koi and pond fish. It has it ALL! Pet Information.
This area gets a whole page about it because it's such a common problem and there are QUITE A FEW solutions. The 
What is Algae? 
If you need pet information AND Koi pondfish and pond information you might like