Nanobubbles vs algaecide: exiting the treadmill
Algaecide removes the bloom you can see and leaves the reason for it: the dead mat sinks, consumes oxygen, and releases its nutrients, setting up the next bloom. That's the monthly cycle. Nanobubble oxygenation changes the conditions instead, so the pond stops favoring the bloom. The chemicals did what the label said; they were never going to do more.
The treadmill, named precisely
Algaecide suppresses the bloom you can see. The dead mat sinks. Decomposing it consumes what oxygen the deep water had left and releases the nutrients the mat was holding. The pond is now lower on oxygen and richer in nutrients than before the treatment: better conditions for the next bloom. Repeat, monthly, indefinitely. Nothing malfunctioned. That is simply what treating a symptom does to a condition.
The structural exit
Restoration changes the conditions in the pond: oxygen held through the full water column keeps the sediment interface aerobic, the internal nutrient feed slows, and the pond's own biology outcompetes the bloom. The pond-algae page walks through the mechanism. The timeline is measured in weeks and seasons rather than applications.
Where chemicals keep their place
Emergency knockdown of a dangerous bloom, under agency guidance, is a legitimate use. And if you've been treating monthly for years, you bought those jugs in good faith. The arithmetic just changes once holding the conditions becomes possible. Bring your annual chemical spend to the assessment; the comparison runs on your invoices.
Tell us what your water is doing.
A specialist reads your description and replies in writing: what it usually means and what we would measure first.