I've had great success with Pond Care Algaefix, it's fish and plant safe. If you want to go a more natural route barley straw bales or extract work well also, albeit, it will take a little longer. A partial water change before doing either wouldn't hurt.

Thank you so much nyrangersimb (z5 NH)… I did a complete water change, scrubbed the liner which was covered with green algae.. .I'm now in the process of making a flower pot filter...I ordered a couple water lilies, a lotus and water hyacinth off ebay… I'm now in need of cattails…here's a picture.

mzrea,

Your pond is beautiful! Nice job.

Thanks butterfly4u!