by Troels Andersen and Oliver Knott
Marsilea hirsuta is well suited to create a low
and dense, green cover in the foreground of the aquarium. This
plant is only a few centimetres tall, it grows slowly and it is
easy to keep, also for the beginner since Marsilea hirsuta
thrives even at very low light. For the expert, the many green
colours and the dense carpet are presenting the tank in a beautiful
way adding a sense of depth in the aquarium.
The scientific name for Marsilea hirsuta(010) is yet to be
resolved although it has been commercially cultivated for decades.
Tropica first produced this plant back in the early 1980s but it
never attained widespread popularity. However, since 2000 the
interest in Marsilea hirsuta has dramatically increased
and today, this plant is very popular amongst aquarist.
Marsilea hirsuta is a water fern belonging to the
Marsileaceae family named after the 18th century Italian
botanist G. Marsili. It originates from Australia but today, the
genus Marsilea is virtually a cosmopolitan. We have often
observed the genus in its natural habitats, for example in Asia,
and here, it is usually the species Marsilea quadrifolia
that occurs. Apart from Marsilea quadrifolia, Marsilea
drummondii is also easily confused with Marsilea
hirsuta. In its natural habitat, it is often found emergent
where it produces longer petioles and divided leaves resembling
clover. This is in contrast to the water form, which has much
shorter petioles and whole leaves or leaves which are only divided
into two or three lobes.
In Tropica, Marsilea hirsuta is also grown emergent and
hence, it is usually supplied with light green clover-like leaves,
which after some time under water are replaced by various other
leaf forms. The water form can produce whole leaves which resemble
a large Glossostigma but it may also set leaves which are divided
into two, three or four lobes of different colours and stature
depending on the actual growth conditions.
When Marsilea hirsuta is planted into the aquarium, you
have to remove the old emergent leaves; these leaves will never
adapt to the underwater environment anyway and thus, they only
serve to absorb vital carbohydrates from the plant during the
transition period to underwater life. From the base, new leaves are
set which initially resemble the emergent leaves and which may be
divided. Later, however, larger and undivided leaves are produced.
From time to time, Marsilea hirsuta produces leaves with
longer petioles and these may be removed if they disturb the
desired picture of the foreground carpet. The pot should be divided
into four to six portions with a scissor and the small blocks may
then be planted into the substrate 3-4 cm apart by using tweezers.
The plant will spend the initial days producing new roots and
subsequently new underwater leaves will also be formed. Thus,
Marsilea hirsuta is yet another example of a foreground
plant which to begin with does not look too impressive, but which
after some time transforms into a dense green carpet.
Marsilea hirsuta tolerates a wide spectrum of light and
CO2 conditions and it grows well in soft as well as hard water in a
wide pH interval. Without CO2 and at low light, the growth of
Marsilea hirsuta almost ceases, whereas it really thrives
at moderate CO2 fertilization at a pH around 7. Marsilea
hirsuta grows best between 20-26 degrees C and longer periods
with higher temperature will often damage the plant.