Last year, I included an Azolla tub in the bioponics system o help soak up any extra nutrients in the system while I learned how to replace fish waste with my own home made liquid fertilizers. It has the double function of providing Azolla as green chicken or quail feed and mulch for the garden in Summer. These are jobs that it has excelled at.
Interestingly, though I only put Azolla (Azolla filiculoides) into that tub, there has been a seasonal succession of plants that has taught me plenty.
In the warmer weather, the Azolla gave way to Duckweed (Lemnacea), a little of which must have been mixed in with it, probably hiding in the roots or leaves. As the Summer reached its end, the Azolla started to die back and was replaced by a thick soup of filamentous algae. Once the cooler weather came back, that started to vanish and the Azolla is back.
I’m planning to keep an eye on this little sub-system over the next two years, observing the oscillation between species as time progresses. I’m not sure if it is the temperature or the amount of sunlight that causes the changes. It could also be that, because the bioponics system is outside and gets a lot of rain falling on it at different times of the year, this is causing a change in the pH of the water and that favours one plant over another. It could also be that because the water (and therefore the amount of nutrients in the system) gets flushed out by heavy rain, nutrient levels fluctuate enough to allow one species to dominate.
It’s all a learning experience!