We struggled with algae coming and going after setting up our new pond. I have a bog with plants just starting to thrive, water lilies and pickerel rush in pots in pond and Mermaid plants, Red ludwigia, and Hornwort in the pond with 5 shubunkins and 12 trap door snails at last count. The water cycles from barely green to dark green to brown based on some change in weather or some other condition. But three things I did that helped was add aeration, slowed down the flow through the bog and reduced feeding of fish to just a very small amount once a day (there is more than enough natural food in ponds to support your fish if you aren’t overstocked).
Lately, water went from soup green, to brown (dead algae) then cleared then turned a translucent green that has now gotten almost gone. I was advised to be patient. I have been patient and things are looking good. Only thing I have added is Prime when ammonia and nitrites spiked to dangerous levels.
I am sure you will get lots of specific advice from the experts here.
