Duckweed 🦆
Duckweed is commonly seen as a problematic weed in aquariums, ponds and waterways the world over because it can take over and create a monoculture. While it's true that it can be a pest, I think it makes a great Bioindicator.
- A species or ecological community that is so closely associated with particular environmental conditions that its presence is indicative of these conditions in a particular environment
It's true that Duckweed can quickly outcompete other plants and block out light but only if it's got the resources to.
An outbreak of duckweed is nature warning you that there is too much food (aka Nitrogen) available! No special test kits required. It's taking advantage of the glut, and reproducing as fast as possible.
The reason it's able to spread so quickly is because it does an exceptional job of absorbing nitrogen from the water. We can use this to our advantage as a tool to remove the excess; all that's required is to remove large chunks of the Duckweed regularly. The aim is not to irradicate it, rather keep it under control until it burns through all the available fuel.
Neglecting to remove runs the risk of creating a feedback loop where the Duckweed smothers other plants which then die and breakdown into food which it then feeds on.