Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants String Algae in shallow stream

5 yr old 800 gal pond - with 2'x50' stream (stream feed from pond to filter falls, elevation 12')
I'm looking for the cheapest chemical to rid the stream of string algae. No Fish - No Plants
I had 8 koi (12-15") up until this past fall...raccoon got them.

I've been using Pool Shock chlorine which works OK...
Looking for other options..

Jeff