Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Azolla problem solved

The Azolla has stayed gone. The aerator was only operating during the day while the sun was strong, and it had to be turned off between Sept. and March due to limited solar power (shared with the cabin), but this did not cause the Azolla to return. There was a small sulfur odor for a few minutes when I turned it back on in April, but nothing like July 2016 when I first plugged it in.

Furthermore, my aquatic plants have recovered and spread—water lilies have self-propagated, and cape pondweed grew back from near-annihilation.

The upshot is that aeration will prevent Azolla, and aeration in combination with thorough skimming will eliminate it.

I made compost with the Azolla that I skimmed, and it turned out well, but I had to greatly boost the N with another material to get up to 150°F for proper decomposition. Azolla is reputed to be high in N because the cyanobacteria within it fix N from the air. However, experience indicates that it will not serve to bring down the C:N ratio to the required 30:1 in combination with straw, as manure will. Hence I do not recommend maintaining Azolla in your pond as a high-N substrate for making compost.

I don't know how important the bacterial pellets are for reducing the muck. I applied them only once this summer, because the pond was no longer a squeaky wheel at our homestead. Time will tell whether aeration sufficiently controls the buildup of muck without a more diligent pellet application regime—more on that later perhaps.