Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Azolla problem solved

More info about the muck: The instructions on the muck-eating bacterial pellets I bought say that the water has to be at least 60�F. Last summer, under the Azolla, it never cracked 60�. The Azolla insulated the pond, and now that it's gone, the pond can heat up enough for the bacteria to thrive.

Before aeration, the pond stratified because the muck was consuming oxygen for decomposition (BOD) at the bottom. Aeration broke up the stratification and increased the dissolved oxygen, but the muck decomposition was still being slowed by the low water temperature. Not only was the Azolla keeping the muck from decomposing faster, it was contributing to it by constantly dying and sinking to the bottom.

Reducing the muck takes more oxygen temporarily. Once it's done, the oxygen level should be higher on its own. There will always be muck, it's just not good to have a thick pile of it.

I theorize that Azolla colonized the pond when the BOD dropped to a certain point. The muck itself may have contributed to the colonization, chemically. I think I have proven that Azolla will not colonize a pond in the presence of adequate oxygen, regardless of a high muck level. I think I have also proven that Azolla will not always go away by itself by just restoring the dissolved oxygen - you probably have to skim it.