the PEA SOUP or single cell algae is definitly going on without the presence of decent filtration. Bio filtration would help combat the amount of algae in the pond and not act as a BANDAID like many of the ALGAE KILLERS in a bottle. The good bio bugs that colonize on filter material compete with the single cell for food. They outnumber the single cell and literally starve them out.
Uv's area topic that is hot on the debate list. Some swear by them... others say they don't do a thing. I'm for the later ,.. except when in some ponds it helps for a fast fix until proper filtration can be installed.
I had a pond that tipped 700 gallons--- complete pea soup in the hot summer temps here in south texas. I installed 2 55gal drums with bio ribbon and 5 filter pads... I took BIO SEEDED pads from another pond and introduced them into the system. I ran a 2200gph external on the system. The pond went from PEA SOUP to CLEAR in 4 days !!! amazing difference !
I have pics somewhere if you'ld like to see them !!
--my ponds--