The bog plant Hygrophila balsamica is native to India and Sri Lanka. In aquaristics it has long been known but is only rarely used for aquarium decoration, as it is poisonous to fish and inverts if its emersed shoots are directly planted in the aquarium.
As soon as it has assumed its submersed form it ceases to be noxious, though, and can be used in a stocked tank without causing problems. Most aquatic plant nurseries cultivate their plants emersed, however, and thus it is easily understandable why this plant is so rare in the hobby. Nowdays common H. balsamica clones from nurseries like Anubias can be used emerged in a tank without problems.
This plant is especially well-suited for tanks with lots of light and a high CO2 content; if there is less intensive light and a lack or a deficiency of CO2 it won't attain its characteristically beautifuly bright green hue, and the leaves stay smaller and have a coarser look.
Apart from these prerequisites, H. balsamica needs iron in abundance, but is not especially demanding given that these basic needs are met.
Propagation is easy. The plant throws a lot of lateral shoots, and even more so if the tip is trimmed. Even floating leaves separated from the main plant may form roots and develop into a plantlet of their own.
Its rapid growth doesn't make it a low-maintenance plant, as it requires frequent trimming at short intervals to maintain its form.
In aquarium layouts, H. balsamica can be used in various ways. For example, its lateral shoots can be totally cut away so the plant grows vertically towards the water surface. This is an wonderful way it can be integrated into the layout especially in Dutch-style tanks. However, by cutting away the tip and thus furthering the formation of lateral shoots you can induce the plant to form a dense bush. And last but not least it is a great "filler plant", especially well-suited for giving dark green plants like e.g. Java fern a background.
All in all you should consider that Hygrophila balsamica can grow into a massive plant and thus needs a lot of space in the aquarium.