I recently purchased some property with a 1 acre spring fed pond with maybe a 2-3 GPM flow into it. At the deepest part it is around 15 ft deep. I have been noticing some stuff floating in the pond near the Dam that is almost sponge like consistency but it falls apart if it is touched. Can anyone help me identify what this stuff is? The pond mud near the dam does not smell good at all and there is a lot of decaying leaves, etc in the water. Thank you for any help.

Tough call. Is the odor like a pig pen? That may indicate, Anabaena, a floating Cyanobacteria.

However the color in some photos looks like an iron bacteria.

Here's a link to a Pond Scum Field guide that may help...

https://www.townofchapelhill.org/home/showdocument?id=28866

I think the above guide is a good point to jump from, but something like this may need to be put under a microscope to help truly identify.

I'm thinking Microcystis.

I have this in my pond as well. It happens only on the really hot days it seems and falls apart to the touch as you mention. Smells terrible as well.

Pig pen would be a good way to describe describe odor. I tested the water and the PH is 6.5 and phosphate, nitrite and ammonia were all low level.

I think I am going to try to use dye and one if those Pond Boss pro bacteria blocks from tractor supply to get some of the decaying matter out. I am curious how long the dye will last since the pond is fed by a slow spring and constantly flowing out as long as the beaver does not start building his dam again.

If you can find barley straw, it is a safe, effective and economical alternative. It won't help with the floating matts but it can be an effective control method.

Just stuff a few pounds of straw into a potato sack, burlap bag or other porous bag. It may need to be weighted so a few inches of the bag is underwater. Anchor to the shoreline, 6 feet or less, in areas of high concentration or randomly in shallow water. An acre pond would require about a dozen.

Flip the bags after 5-7 days and replace after 2 weeks.

Just curious, what do you mean by ammonia being low?

I will do some research on the barley and see if I can fond some.

As far as ammonia being low I just mean it tested at 0 PPM

Noel, thanks for posting that resource.

P.S. If I had written that guide, then I would definitely include the line "Pond Scum Expert" on my tombstone.

I had this too in my pond at the end of summer. I just bought the property (Central Virginia) so I have little understanding of any pond care prior to purchasing it. Did y'all ever figure out for sure what this is and how to mitigate it?