Green water, green gunk, stringy algae, green slime is all caused by
too much sun, fresh water, fish waste, fertilized run off, rotting
plants and blown in dirt.
In new ponds and spring ponds algae is always the first thing to start
growing.
The best defense against algae is to have lots of plants to compete for
the nutrients, few fish, not overfeeding those fish, some shade and
cleaning up debris.
So not use algaecides, they only make lots of suddenly dead algae to
feed the next algae bloom. Gently remove string algae. Don't worry
about fuzzy algae that grows on the sides of things this is good for
the pond.
You can purchase an Ultra Violet light set up to eliminate suspended
algae (green water), running the water under the light. It does not
work on string algae or floating gunk and slime.
Filtering with plants works well. I run my water into a stock tank
topped with water hyacinth and down a waterfall planted with
watercress.Others on rec.ponds have wonderful veggie filters.
Most algae blooms (green water) will pass within a couple of weeks.
Time and patience is key.
Remember patience...

kathy :-)
www.blogfromthebog.com