Freshwater

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Part III: Water, Chemicals, and Plants
Plant Types
You can find three basic types of plants in an aquarium shop: aquatic, marginal,
and terrestrial. Unfortunately, many dealers sell terrestrial (grow-in-theearth)
plants as aquatic plants. Each type of plant is unique in its requirements
for survival and growth, so you need to know exactly which species you can
accommodate before you purchase any plants. Make sure each plant type is
labeled correctly before you take it home! (Chapter 17 gives you good examples
of live aquatic plants that you can enjoy in your home aquarium without
having to worry about them too much.)
Aquatic plants can be entirely submerged beneath the water line of your tank
and still survive. These plants die when they are removed from the water.
Sagittaria (Sagittaria natans) and pygmy sword (Echinodorus quadricostatus)
are two good examples of aquatic plants.
Marginal plants spend only part of their time submerged beneath the water.
These types of plants flower and seed out of water during the dry periods of
the year. Examples of marginal plants include cryptocoryne (Cryptocoryne
balansae). Marginal plants require special handling and should be left in the
hands of expert hobbyists.
Terrestrial plants live on land and do not survive very long if they’re completely
submerged. We do not recommend them for use in the home aquarium.
Let’s proceed to the more common kinds of aquatic plants, the ones that are
used most in home aquariums.
Floating plants
Floating plants do not anchor themselves and drift around the top of your
aquarium. Floating plants can grow very quickly, so you need to thin them
out — or prune them — when they become too thick and bushy. If you don’t,
they may block out the light that enters your aquarium from the hood. The
resulting loss of light can lower the temperature of your aquarium water,
which has a devastating effect on the health of your fish and plants. Floating
plants reproduce easily by sprouting young daughter plants and propagating
new plants from severed pieces. Use floating plants in spawning tanks to hide
young fry.
One plant in particular, duckweed (lemna), multiplies so rapidly that your
tank may look like the lights have burnt out permanently. Avoid buying duckweed
unless you have time to prune it back. Another floating plant is the
water lettuce (Pistia stratiotes).