This is a spectacular native Australian aquatic fern, which is similar to Bolbitis in the aquarium. It is one of a small handful of native water fern species, and is a very easy species to grow, with vibrant green leaves and translucent new growth.
The leaves of this attractive water fern look very similar to Bolbitis heudelotii, but with wider lobes (pinna) on the fronds. These finely divided fronds are also a translucent green colour and have a hard, firm feel to them. Similar to Leptochilus (Java Fern), the growing leaf tips start off more translucent and darker green, which eventually fill in as the plant grows. The fronds of the Australian Water Fern grow to 10-20cm in the aquarium, and so it is a versatile choice for most aquarium sizes.
In contrast to Bolbitis, Diplazium dilatatum is a rosette plant, and does not grow with a creeping rhizome. Mature plants will grow a dense rosette of 15 leaves or more. In this way it can be used similarly to an Echinodorus in the aquarium: as a centrepiece or midground plant. The roots are not adhesive like Bolbitis or Leptochilus (Java Fern), and so can be buried in the substrate. Ensure the crown remains above the surface of the substrate. Grown underwater however, this species does appear to primarily absorb nutrients from the water column through its leaves, and so planting it in the substrate is not entirely necessary.
In terms of care, Diplazium dilatatum is relatively undemanding. It thrives in a variety of water conditions, from soft to hard water, and we can recommend a pH of 5.5 to 8. Ideal water temperatures for this fern range between 17°C and 28°C, making it suitable for most tropical aquarium setups. This fern will tolerate low light conditions but will also grow well in high light setups. For optimal growth under high light, supplementing with additional CO2 is recommended.
Propagation of the Australian Water Fern is also very easy. This is a unique species which propagates similar to Cryptocoryne or Helanthium species. The plant sends out long runner roots, from which new ferns grow. You can either let these grow where they are, or, once these small ferns grow large enough you can simply separate them off the main plant and replant them in a new location within the tank. Over time, the separated piece will grow into a new plant, expanding the fern's presence within the aquarium.
Diplazium dilatatum is native to Queensland and parts of NSW, as well as Asia. It can also be grown emerse, around ponds in shaded areas as far south as Sydney. When grown out of water this plant looks vastly different, growing 1.5-2m in height with long green fronds that are 80–150cm long. It is a species that has adapted to live in areas that flood or are inundated seasonally, and spends months underwater in its natural habitat, particularly in Queensland, Malaysia and Indonesia.
Diplazium dilatatum is a stunning and versatile aquatic plant that will make a great addition to most aquariums, and is an especially great fit for native and biotope aquariums.