Common Duckweed (Lemna Minor), is a small floating plant that has 1-3 leaves and 1/16" - 1/8" long. Freshwater, easy to grow and maintain. You can use this small portion as a starter culture. They propagate fast under good lighting and cover the water surface like a green carpet.
Because of their impressive growth rate, they act as one of the best water purifiers that you can find for a fish tank and can be invaluable to newly established aquariums that are having water quality problems. And if cleaning and purifying your aquarium’s water isn’t enough, they also have a well-deserved reputation for reducing algae growth.
To take the duckweed out from a Ziploc shipping bag, add some water to the bag and empty it out into a bucket of water, using two forks to gently separate / untangle the duckweed. With a fork, transfer the floating duckweed to a tank with old aquarium water
NOTE: Each portion is roughly 1-2oz