I humbly request any suggestions that may aid in our current struggle:
I work at a school in Northeastern Florida, and I inherited the care of 2 small ponds, located at the entrance to one of our buildings. The ponds are about 6.5-7 feet around, and about 2.5-3 feet deep when full. The only permanent residents are goldfish, which we've kept (relatively) successfully for a couple years.
For some reason, these ponds were built without filters- only water pumps. The pumps just power the waterfalls.
We've slowly grown more and more dark, black algae, which is beginning to take over, and looks pretty unsightly. That algae, I assume, is aiding in filtration in a major way, because... as mentioned, the ponds were made without filters.
In an effort to provide some sort of functional mechanical/biological filtration, I put together a crude system which somewhat works, a little, and is better than nothing: I ordered 200 plastic pot scrubbers off Amazon, along with mesh bags. I filled the mesh bags with the pot scrubbers. I cut the bottom off a large plastic crate, filled the crate with the bagged pot scrubbers, and placed the whole thing over the pump. I then put rocks on top of the sponge-filled crate to hold everything down (these components, along with the ponds themselves, are pictured below).
I hoped these "filters" would work, sucking the water through the bags of sponges on it's way in, and coming out and over the waterfall "clean".
And I think they are working, to an extent. Any time I go in to gently clean them, they're covered in the delightful brown sludge- seemingly housing a thriving colony of beneficial bacteria.
But I just don't think it's enough.
The ponds have tons of algae. And I know- goldfish produce a lot of dirty waste. The ponds are both covered by a roof, meaning- because of the shape of their build and their location- even in the peak of summer, they only receive a few hours of indirect sunlight per day. This has made growing plants challenging (I also just may not be great at growing plants in a pond). I did manage to add some Canna Lilies, a Peace Lily, and a few epiphytes, which do what they can to help.
As you can see from the picture, the pH is testing at LEAST at an 8.8. An ammonia test, however, revealed very little ammonia (assuming I performed the test accurately- dip the strip completely in and out of the water for 30 seconds, check reading).
I've tried hooking up a canister filter, but the fact that the ponds are (slightly) lower than ground level, made it very difficult, almost impossible, to get it to run properly.
I own 1 aquarium that's run fairly successfully for a few years now, but don't have any experience with ponds, other than what I've learned trying to help out with these 2.
I appreciate everyone's time, and will gratefully accept and try any potential solutions.
