This looks like Filamentous Algae, but let's see if someone will confirm that.
If it's gathered around the perimeter, a garden rake can remove quite a bit of it, although it's labor intensive. In a current pond I'm helping with, the FA just seems to regenerate quickly. The pond I'm talking about had it's dam cut last summer, and refilled in the later summer of 2021, so we're thinking the FA is just coming from all the leaves that were accumulated on the pond basin, but we really don't know.
You can also use Cutrine or Copper Sulfate on these mats of FA. If you put Copper Sulfate on them, I've found that it just sinks the mat from where it was floating. While this isn't a huge problem, you may have fish spawning under those mats, and dropping the mats on the spawning bed, along with the presence of Copper Sulfate, may prevent that spawning nest from producing.
Excerpt from Robert Crais' "The Monkey's Raincoat:" "She took another microscopic bite of her sandwich, then pushed it away. Maybe she absorbed nutrients from her surroundings."
Also, if you do rake some out, you cannot leave it on the bank (long term) to eventually wash back into the pond. You need those nutrients OUT of your pond cycle.
We've had the same issue with our rebuild. When it was drained it had quite a rich growth of terrestrial plants on the bottom. It also seemed like the areas near the banks were very nutrient rich and as the pond filled, the FA came on strong.
Things we've done since the first mega bloom, one or more of which seems to have helped: aeration, pond dye, muck reducer and cutrine.
It has receded from covering about a third of the surface to being mostly confined along the banks and corners now.
The liquid cutrine showed results but that was temporary. The granular I put down in the corners seemed to have no effect as far as what was on the surface. The raking works and is also temporary and as far as it appears to me, the muck is drying up and staying on the banks. You can also haul it away if you want.
A couple days ago for fun, a 2 inch trash pump I had set up in one corner to water my gardens I used with a firehose nozzle to mega blast the moss that was stacked up in that corner. I blasted it back down to the bottom.
The algae doesn't seem to produce quite like it was several weeks ago. I'm not an expert by any means but just wanted to share some of the things I've tried.
Best, laziest way is to whack it back with Cutrine Plus liquid and granular (they are formulated to work in 2 different areas of the pond) and then where legal stock Tilapia to eat the new stuff that grows. We've found in Northern Indiana that stocking 40#/surface acre is needed.
Other options have been covered, but note that with an algaecide you will most likely need to retreat the pond every 2 weeks when the FA is growing.
For dealing with that floating FA around the perimeter, killing it is quick and easy however sending it as dead plant material to the bottom allows it to decompose and put ALL the incorporated or bound nutrients that grew the algae back into the pond basin - a recycling process None of the nutrients / elements that allowed the algae to grow were removed from the pond basin. The only thing added or net gain to the pond system was the chemical algaecide that killed the algae.
Best pond and beneficial management is to actually remove or harvest the algae. Harvest the crop that grew. A very useful tool for removing FA is a long handled smelt dipping net. This removal reduces the offending nutrients in the pond, the cause of algae, and lessens the amount of oxygen that was consumed in decomposing the dead algae. This helps keep the pond at a lower nutrient level. Removing the algae and associated nutrients reduces the total nutrient load in the pond helping to keep the pond at a lower nutrient level. Nature's way or process is to keep adding MORE nutrients to the pond basin to grow MORE plants that grow and die in the pond to eventually fill the pond with dead material until the pond once again is dry land - this is called aquatic succession. see more below
Another option to removing or reducing the algae is to get something to eat the algae and then remove the "critter" that ate the algae. A form of harvest. Then some of those nutrients that grew the algae are removed (HARVESTED) from the pond basin. Think of sheep or cows grazing on the pasture, then harvest the animals. Constantly removing a harvest crop from farmed land without adding nutrients back to the land will eventually grow less and less crop volume. Nutrients need to be added to harvested crop land to keep the soil productive. This concept also works in the aquatic system - a pond. Harvest or lack of harvest of things that grow in a pond affects the pond's productivity and ability to grow plants and animals. The more nutrients that enter a pond basin the more plants that will grow in that pond basin to eventually over time fill that basin with MORE nutrient / silt accumulation and dead organic materials - aquatic succession.
What I did not see in his reply is how much work "harvesting" that stuff is. It is very heavy. I drug a lot of it out and loaded it into a trailer one year. Was not a lot of fun. Does build muscles though, if it doesn't break your back first.
I think on the second page are pictures of the rake I made from a landscape rake to pull it out of the pond that worked pretty good.
A long while ago I saw someone remove algae by making about an 10' x 20' construction using large opening plastic screen material between two 10' or so long metal rods, and a set of chains on the rods intended to be dragged under the algae when "cast" from out in the water via boat (or opposite bank). The off-shore rod is then pulled up and over the top surface when pulled back out by a winch on a tractor. I don't recall how the rod in the deeps was pulled up then over, if it were the people in the boat or a float or... I was a kid. Some plants squeezed out the sides when pulled in as it compressed, but a lot of it was captured and dragged off while captured fish were rescued and thrown back in. There could certainly be improvements in this method, but the simple weight of algae on algae helped to compress a lot of water out. Most of the weight is captured water, and why it weighs so dang much.
There was a algae bloom in the cottages where we were staying, and that was the solution to be able to get boats in and out. Years later I learned were were swimming in this literal shit, as human sewage was being dumped into the same small bay. No wonder my immune system rocks.
Probably not so good for the small fish population.
Bill, do crawfish help against algae? I know tilapia do & would love to harvest them, but this has proven difficult as they don't seem to bite anything I throw. Even Stubby Steves!
A long while ago I saw someone remove algae by making about an 10' x 20' construction using large opening plastic screen material between two 10' or so long metal rods, and a set of chains on the rods intended to be dragged under the algae when "cast" from out in the water via boat (or opposite bank). The off-shore rod is then pulled up and over the top surface when pulled back out by a winch on a tractor. I don't recall how the rod in the deeps was pulled up then over, if it were the people in the boat or a float or... I was a kid. Some plants squeezed out the sides when pulled in as it compressed, but a lot of it was captured and dragged off while captured fish were rescued and thrown back in. There could certainly be improvements in this method, but the simple weight of algae on algae helped to compress a lot of water out. Most of the weight is captured water, and why it weighs so dang much.
There was a algae bloom in the cottages where we were staying, and that was the solution to be able to get boats in and out. Years later I learned were were swimming in this literal shit, as human sewage was being dumped into the same small bay. No wonder my immune system rocks.
Probably not so good for the small fish population.
I tried dragging out some junk but it captured to many shrimp and a few dads…. So I gave up It was a grappling hook so it didn’t drag much but full of shrimp
The junk was slender spike rush that has taken over out to 6’!