I struggle with scummy floaty "stuff" in my 1/4 acre pond. It looks much like yours, often, during the warmest parts of the summer. This is my uneducated guess as to what is going on with my funky outbreaks...
My pond's info,
- 1/4 acre, 10 foot deep with mostly steep banks.
- Excessive water shed (about 20 plus acres) that really flushes the pond in the spring and sometimes fall.
- 24/7 aeration, about 4 turnovers pew day(does not run during the winter months).
- Muddy from crawdads and possible ground water run-in (even though it is not a ground water pond).
- No submerged vegetation. Likely due to the muddy waters.
- Ample emergent vegetation along the 100' dam, but little elsewhere due to the steepness and young age of pond.
- Previous water tests show low to non-existent nitrates, ammonia, or phosphates...PH consistently between 7 and 8.
- Very little wind action and limited sunlight due to being surrounded by trees on 2 sides and a rather high dam on the third side. Rain or wind action can dispel a surface outbreak for a day or so, but once this action ceases...it comes back quickly during the hot months.
I believe there is enough nutrients in the pond as a whole to support blooms of various kinds, but not enough clarity to support them much below the surface. Due to the aeration, these blooming organisms get exposed to the surface and grow enough to "head to the light" or surface where they float and prosper, and often get really nasty looking. Once the heat of the summer passes, the pond stays mirror like on the surface.
Keep in mind I said "uneducated", but the above are my moderately experienced thoughts on the topic.
Here's a nice guide to pond scums that might help...
https://www.townofchapelhill.org/home/showdocument?id=28866I have often thought about clearing the water with Alum (or whatever) to promote some submerged plant life, but I have not convinced myself the money and effort would pay off due to the excessive water throughput. I do trap out the crawdads daily during the summer months (for the last 2 years) and I have seen no clarity improvements even though I took out over 1500 last year and over 1000 this year (3-5 inches long).
