One sandwich filled to a half inch thickness. Should cover the top of a 28 or 20L tank. Great food source for goldfish and other plant eating fish.

Duckweed (Lemna minor) is a tiny, fast-growing floating aquatic plant ideal for ponds and aquariums, offering excellent natural filtration, shade, and a high-protein food source for fish. It thrives in full sun, easily covering water surfaces in dense, bright green mats that reduce algae growth, but it requires regular management to prevent rapid overgrowth.