Although grass carp are used to control many aquatic weed species, this fish WILL NOT effectively control the growth of water pennywort. Mosquito fern is a small, free-floating fern often found in large colonies that can completely cover small ponds or lakes. The leaves vary in color from green to red. The plant can grow equally well free-floating or rooted in the soil. When floating, it can rapidly reproduce by vegetative means and can completely cover the pond surface quickly.
Young plants are green, but as they mature they change to red and then brown.
Complete coverage by mosquito fern is a serious risk to fish by reducing sunlight penetration into the water, which decreases oxygen production. The plants also hinder fishing and other water-related activities. Chemical Control You can control mosquito fern by using the same treatment methods recommended for duckweeds. Read and follow label instructions before using any chemical in water. Dilute with water and spray evenly over pond surface.