I like to use floating plants during initial set up of a new aquarium. They can absorb nutrients from water column thus preventing algae growth. However, too many duckweed can block the lights which is essential for the plant growth. Sometimes, it can take over your aquarium.
You can remove them manually with fish nets.
It’s not always easy to remove all duckweeds from the aquarium as one single plant can grow into a big column. A simple DIY surface skimmer can be useful. It can be made with an aquarium powerhead and a water bottle with bottom cut out. A piece of sponge filter and filter floss can be added to the surface skimmer to collect the duck weeds.
