It is possible to have a clear pond without using any chemicals
at all. (which is a relief for those of us whose brains freeze at
'1 teaspoon per gallon')

Our ponds are nutrient heavy. We have WAY too many fish in
our ponds than Mother Nature recommends.
Like the other posters
recommended higher order plants are the way to use up the extra
nutrients.
Ways to cut down on nutrients is to cull the fish population,
stop feeding the fish as much and use a filter to screen and convert
fish waste.

Fresh water is a nutrient for algae and you've had more than your
share of fresh water this year. There isn't much you can do about
that.

Algae and string algae are very efficent at growing when the higher
order plants are still waking up. Spring is usually a time when ponds
will suffer an algae bloom.

I use watercress in the spring to get ahead of the algae. I place stems
of it (from the grocery store) under a rock (one stem to a rock) in my
waterfall. The stuff loves fast running, cool water. It spreads but the
roots
are shallow and brittle and it is very easy to rip up. I have
watercress that
wintered over, frozen in the ice, that is growing like crazy right now
and
the only other plant growth out there is two inch high iris.

The problem with algaecides is that they make lots of suddenly dead
algae which feeds the next algae bloom.

Your pond isn't old enough to need cleaning yet, but dead plant matter,
fish waste, mulm, muck and crud are also good food for algae.

And finally sun. Floating plants will shade the water, like lily pads.
Water hyacinth are
good floaters in that they reproduce like crazy. In zone 7, where we
are,
they don't survive the winter so have to be taken out as with their
demise
they will turn into decaying plants (more algae food).

Patience is always helpful. Frustrating, but helpful.
It takes a while to get to know your system and how to
manage it.
good luck!

kathy :-)