What you have growing is Filamentous Algae (FA). It's a good indicator that you have a very fertile pond. However, depending on how deep the pond is, it can eventually cover the entire surface. It grows on the bottom out to about 4' deep and as it dies off, air is trapped in the filaments and causes it to float.
It will eventually turn black and then sink back to the bottom, where turns into nutrients for more algae to grow. It typically grows stronger in the cooler months.
Whether it's a good thing or bad thing I think is a matter of opinion. If your pond gets deep enough, fast enough, to keep it on the shoreline, you can choose to leave it alone. It provides some shade and cover for your fish. It does create a little dissolved oxygen, but uses it all and more up again as it dies and respirates at night.
I believe every pond as some degree of FA. You can manually remove it by raking it out, or you can treat it chemically if you decide you want it gone.
.10 surface acre pond, 10.5 foot deep. SW LA. The epitome of a mutt pond. BG, LMB, GSF, RES, BH, Warmouth, Longear Sunfish, Gambusia,Mud Minnows, Crappie, and now shiners!!...I subscribe!!
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