Pond Boss Forums INTRO New Forum Member Introduction New member in Charlotte NC

Hello. Have had a small 150ish gallon pond for 10 years in backyard. Always develop green colored water, so drain about 80% of water(leaving fish in) 2x/year. Then check/adjust ph as needed using strips from spa. And NOT chlorine chemicals.
The submerged filter used (300 gph) has mesh layer and media, but about 5 years old. I realize there is no UV light. The goldfish seem healthy, and have yet(knocking on wood) to lose more than 2-4 each year. They seem to breed enough to keep numbers between 10-15/year. I use a bubler at one end, with the filter sitting at other end, and tube spraying water thru a fishhead mouth(antiquey).
The sun bakes on it during summer, and the 4 lillies/hogwort plants seem to reduce sunlight. But this year, after a new liner install and water there is green water already. I'm thinking about a new all in one filter system w/UV light and spray and another group of plants.
Your thoughts are/will be appreciated.
Thanks for being here...

Sounds like it may be a perfectly normal algal bloom.

That does require sunlight. If not too ugly for your pond location, could you put up a sun shade of some sort? You might also need some side shade, since photosynthesizing organisms can keep growing on surprisingly little sunlight.

Adding more water plants may help, since they compete for the same nutrients in the water as the algae. Another option would be a floating island of aquatic plants. That would block some sun AND the roots would be taking up nutrients.

Are threadfin shad available in your area? They can actually filter and eat the algae. You might have to cull them if they do get big enough to eat small goldfish.

My crazy ideas above may be better suited for slightly larger ponds. If feasible, the UV light system my be sufficient to kill all of the algae that grows in your pond. Do your goldfish eat anything natural in your pond, or only eat your feed? The UV would also kill most of the small organisms that are natural food.

Good luck on your small pond project!