A HORRIBLE idea for a pond intended for sport fishing is as follows:
Cowdung is commonly used as a fertilizer for fish ponds in India but fish production is limited to 15002000 kg/ha. These yields can, however, be more than doubled if the dung is first fed to a biogas plant and the digested slurry then used instead of the raw dung.
MUCH Much much more likely is this:
Excessive algae growth is one of the most common problems occurring in ponds. Traditional mechanical and chemical control methods are not always efficient or economical.
In recent years, the use of barley straw has become more common as an alternative method for controlling excessive algae growth. This method has been extensively studied by Dr. Jonathan Newman at the Centre for Aquatic Plant Management in Great Britain. When applied at the proper time and rate, barley straw has been a very successful algae control techniques.
Barley straw does not kill existing algae, but it inhibits the new growth of algae. The exact mechanism is poorly understood, but it seems that barley straw, when exposed to sunlight and in the presence of oxygen, produces a chemical that inhibits algae growth.
It is likely you can get more than enough information from the highlighted source. I don't know where this Centre is?