Primarily, they help maintain optimum water conditions by absorbing carbon dioxide and, to some degree, remove nitrates from the water.
In addition, they provide fish with shelter, spawning sites and, in some cases, food!
In the aquarium, you have the choice of using real living plants or equally realistic plastic replicas; either will beautify the aquarium and whilst the plastic ones won't contribute any water-cleansing functions, they still make the aquarium look nice if you like to keep fish that have strong vegetarian-diet tendencies!
Live aquatic plants are usually classified by hobbyists into three groups:
Rooted, Floating and 'Cuttings'
Rooted : these plants generally feed through their leaves but have roots for
merely anchorage purposes. Another way of anchoring themselves in
position is by clinging on to rocks or logs with thin creeping stems.
Most rooted plants send out vegetative runners on which young plants
grow; alternatively, some have 'daughter plants' growing on leaf
Members of the Aponogeton genus bear aerial flowers which, when
pollinated, produce seeds from which extra plants can be grown.
Single, large specimens of rooted plants are best used as 'feature plants' in aquascaping designs, whilst the tall, grassy species provide natural 'curtains' which hide the back and side walls of the tank.
Floating : As the name suggests, these plants are happy to float around
untethered. Some have nutrient- collecting, trailing roots dangling down
into the water and these make excellent refuges for young fish.
Surface floating plants often become rampant and should be netted off
Floating plants offer shade, shelter and, sometimes, bubblenest building material for fishes.
'Cuttings' : Fast growing, bushy plants can be propagated by taking cuttings and
using these to make more plants by re-anchoring them in the
substrate. Fine-leaved species such as Cabomba and Myriophyllum are
examples of such plants.
These plants provide an excellent and natural way to fill up corners and spaces when aquascaping the aquarium. Dense bunches of such plants also make excellent spawning materials for egg-scattering fish.
© FBAS RCM/RDEAquarium Management Sheet 10 1/2