Hygrophila corymbosa

Hygrophila corymbosa, commonly known as temple plant, starhorn or giant hygro, is an aquatic plant in the acanthus family. It is native to South East Asia, but is grown worldwide in tropical aquariums. The plant naturally grows as an emergent, but it can survive long periods fully submerged.
Cultivation.
"Hygrophila corymbosa" is a fast-growing plant that can be frequently trimmed back. It prefers a well-lit situation, a nutriment-rich water and compost, and benefits from additional CO2. If it is allowed to grow out of the aquarium, it will bear purple scented flowers, often causing the lower leaves to drop. The plant is adaptable to a variety of water conditions. There are several forms in the aquarium trade such as "red", "siamensis" and many others, that seem to be mainly ecological variants.
It can be easily propagated by taking cuttings and planting them in the substrate. The plant is reported to be useful for absorbing ammonium and nitrates and helping to fight algal growth.