By Rhett Butler
Live aquarium plants are a worthwhile addition to the fish tank. In a well planted tank, the fish have better colors,
live a more natural life, and appear more comfortable than in an unplanted tank. Though they need more care than
plastic replicas, live plants can be kept with few problems as long as there is plenty of light and no plant-eating
or plant-destroying fish.
Photosynthesis is the process by which plants convert carbon dioxide gas and water are converted with the help
of light energy into glucose (energy) and oxygen gas. This process can be expressed in the equation:
6CO2 + 6H2O + sunlight => C6H12O6 + 6O2
Thus in an aquarium during the day, plants use the carbon dioxide, produced by fish, and water to produce oxygen
and energy. The oxygen is used by fish for respiration. At night, there is no sunlight or artificial light to no photosynthesis takes place.
Follow the suggestions under "Gravel" in theaquarium section for gravel set-up. In most cases,
plants do best in fine gravel with some sort of base fertilizer. Base fertilizer is not required, but is recommended.
Iron rich clay fertilizers like laterite, and other fertilizers manufactured for aquatic plants are suitable.
One of the most important ingredients to a successful plant aquarium is strong lighting. As a general rule, 2-3
watts per gallon is sufficient for a well-planted aquarium. Often light is measured on a scale of lux. The following
table gives the light requirements in terms of lux for plants growing at different water levels:
||Cryptocoryne, Vesicularia dubyana
||Cabomba, Lemma, Salvinia
Fluorescent bulbs have proven to be the most practical bulb for lighting planted tanks. However, in tanks deeper
than 20" (50 cm), most fluorescent bulbs are not strong enough to illuminate the tank sufficiently, so mercury
vapor lamps can be used. For mercury vapor lamps, use about 6.25 watts per inch (2.5 cm) of tank length.
Be aware that the intensity of fluorescent tubes decreases subtly, with time. Thus one tube should be replaced
every six months.
Most aquarium plants can be kept in water with a hardness from 4-12 dH, and a pH from 6.5-7.2. For specific species,
see the individual descriptions. The water should be kept as clean and clear as possible because free debris can
settle on plant leaves or cloud the water, interfering with light intensity. Very few aquatic plant species can
survive in brackish water.
Plants require macro- and micro nutrients to grow. Macro nutrients are substances that are required in relatively
large amounts such as nitrates, phosphates, and sulfates. These nutrients usually occur naturally in the aquarium
from tap water and fish. When these levels rise to excessive amounts, an "algae bloom" can result. Nitrate
levels rise do to their production by fish. Thus these macro nutrients need not be added to the aquarium.
Micro nutrients are elements that are required in trace amounts. Micro nutrients important to plants include copper,
iron, manganese, boron, zinc, and calcium. These elements are needed in only the smallest amounts, and excess can
The following table reviews some of the major nutrients important to aquatic plant growth. (The macro nutrients
are marked with an asterisk*)
Nutrient - Function
- Carbon* - the basic block of carbohydrates, which plants use for energy
- Oxygen* - important in plant respiration at night
- Hydrogen - (in the form of water) is needed for nutrient transport, among other
- Nitrogen* - (usually in the form of ammonia or nitrate) necessary for protein
- Phosphorous* - promotes flower development
- Sulfur* - used in protein synthesis
- Iron - used in chloroplast formation (chloroplasts are the structure in which
When there is a deficiency of nutrients, the plants suffer. If the leaves yellow faster than usual, there could
be a deficiency of nitrogen or sulfur. If the leaves yellow starting at the tips or the leafs seem especially brittle,
an iron deficiency should be suspect. Evidence of an over fertilization of iron or a manganese, phosphorous, or
potassium deficiency is yellow spots on the leaves.
Because macro nutrients are usually available naturally in tanks, an all-around plant fertilizer cannot be recommended
for aquarium plants. Instead use preparations of "trace elements" which are specially prepared for aquatic
plants and are widely available in pet stores. Never overdose with a fertilizer because plants and fish can be
damaged. Do not purchase a fertilizer than includes phosphate or nitrate, because horrible algae problems may arise.
Fertilizers are commonly available in liquid and pelleted forms.
Carbon dioxide is used by plants for photosynthesis and is a fundamental compound to the success of a planted aquarium.
Carbon dioxide is present in aquariums as a byproduct of fish respiration and nitrification, and dissolved in the
water from the atmosphere. Carbon dioxide levels should range from 5-15 Mg/l, once the level surpasses 20 Mg/l,
fish may be harmed. Remember that aerating the water quickly causes carbon dioxide levels to decrease. If the tank
is heavily planted and lightly stocked with fish, or if the water is hard, carbon dioxide fertilization may be
necessary. However, carbon dioxide fertilization is usually not required for a beautifully planted aquarium. Carbon
dioxide can be added to the fish tank using a carbon dioxide fertilizing system. Carbon dioxide fertilization is
more popular outside the United States than it is within.
Almost any filtration system (mentioned in theaquarium section) will work in a plant tank. The
main requirements of the filtration system are: 1) that it does not create much water disturbance, because precious
carbon dioxide will be lost; (2) that the filter remove floating particles that may block the lighting or settle
on plant leaves; (3) and that the filter create some current to keep nutrients moving through the water and to
prevent debris from settling on leaves.
Undergravel filters are not the best choice because the air bubbles create surface disturbance and the filter plate
limits substrate size and composition.
Before planting the aquarium, make a rough sketch of how the tank should look. Include rocks and wood structures
and plants so that there is a plan to follow.
Plants fall into different categories as to how tall they grow and their shape:
Foreground: Foreground plants are small, low growing species that often form carpet-like mattings by producing
numerous runner plants. Foreground plants often inhabit shallow water and may require bright lighting. Plant foreground
plants in front of middle ground and background plants.
Middle ground: Middle ground plants are medium sized species that can be used behind foreground plants, but in
front of background plants. Middle ground plants can block unsightly stems of background plants.
Background: Background plants are usually tall and can be used to block out heaters, filters, hoses, and wires.
Background plants are generally fast-growing species that require less light than foreground and middle ground
Bunch Plants: Bunch plants are usually middle ground or background species that look good in groups of several.
Bunch plants are often easily propagated by cuttings.
Specimen Plants: Specimen plants are usually large, decorative species that are planted singly in the middle ground
or background. Specimen plants are often used as a focal point and may be highlighted with a spot-light.
Contrast Plants: Different-looking plants can be used as a contrast to the other plants in the tank. Red-leafed
plants can be used as a color contrast to green plants, while plants with pointed leaves can be used as a shape
contrast to those with large round leaves. When contrasting plants, place plants with similarities in color, size,
or shape away from one another, while planting plants with differences closer together.
Floating Plants: Floating plants require plenty of light, but must protected from leaf burn by leaving distance
between them and the bulb. Floating plants often propagate very quickly by division and in a short matter of time,
take over and aquarium and block out light. Floating plants should be kept out of the light path of plants below
that require a lot of light.
Plants have several means of reproducing. Some species reproduce amazingly fast, taking over an entire tank in
a matter of weeks, while others do not appear to propagate themselves at all.
Cuttings: Cuttings are the easiest way to propagate plants. Simple cut a lengthy
(6-8") section of stalk from the plant and plant it in the gravel. Plant cuttings with at least 1" (2.5 cm) of the stem under the substrate. Remove the leaves on the section
that will be in the substrate. Plant tubers and bulbs at a 45° angle in the substrate with the growing tip
pointing out of the gravel. Both the cutting and the original plant
should continue to grow. Most bunch plants can reproduce by cuttings.
Runners: Many aquarium plants, especially foreground and Sword plant species produce outgrowths known as runners.
These new shoots are formed on stems and usually grow along the substrate or within the substrate. Plants that
reproduce by runners (daughter plants), are often prolific.
Rhizome: The roots of some plants produce side-shoots. These plants can be propagated by cutting the rhizome into
pieces. Be sure to include some leaves and some roots with the rhizome. Replant the cut sections along the surface
of the substrate. These sections should root.
Adventitious plants: Adventitious plants are plantlets that arise from the mother plant. The mother plant produces
a number of plantlets with drift free of the mother plant, and root on their own. Adventitious plants will either
be released by the mother plant or can be cut when the plantlets reach a suitable size. Also referred to as "division."
Seeds: Plants that flower produce seeds only after pollination, in nature, usually be insects. In aquaria, use
a fine brush to transfer pollen from the stamens to the stigmas.
Like land plants, aquarium plants need to be pruned and thinned on a regular basis. Many of the taller, stalky
species will actually grow out of the water if they are left unpruned. Other tall species will grow along the water
surface and block out light to lower species if they are not trimmed. Prunings of many species, can be replanted.
With leafy plants, like Swords, the large, outer leaves may need to be removed to make room for new growth. Plants
with floating leaves like Nymphaea species, need to be cut back so that the light is not blocked from lower plants.
Cut the upper leaves until only the lower leaves remain. When plant branches become dense, they should be thinned
by removing some branches.
Plants to avoid
There are several plants sold as aquatic plants in pet stores that are not actually aquatic. These plants do not
grow for long underwater and eventually end up polluting the tank when they die. Among some of the commonly available
nonaquatic species are: Aglaonema, Brazilian Sword, Cherry Hedge, Draceana (Princess Pine), Green Hedge, Mondo
Grass, and "palms."
Almost every aquarium is plagued at some point by an "algae bloom." "Algae blooms" can be fueled
by excess light, especially sunlight, and excess nutrients, especially nitrate and phosphate buildup. Thus "algae
blooms" can often be prevented by regular water changes and placing the tank away from direct sunlight. There
are several types of algae common in the aquarium:
Green thread (filamentous) algae: Green thread algae forms long, green, filaments
which often grow from plants. Thread algae needs abundant light to thrive. Thread algae can be damaging to the
aquarium by taking important nutrients that aquarium plants require. Thread algae can be controlled by algae-eating
fish or by manual removal.
Pelt algae: Pelt algae adheres to plant leaves by a single filament an reaches a length of 0.8" (2 cm). Pelt
algae usually develop in water with a high nitrate content and can cause plant leaves to die. To eradicate pelt
algae, remove the filaments manually, introduce algae-eaters (Flying Foxes) or snails (ramshorn). Regular water
changes slow pelt algae growth.
Suspended algae: Suspended algae usually resembles green water and is comprised of Volvox. Suspended algae is most
commonly introduced when pond foods are fed. Suspended algae can be removed by a series of large water changes,
filtering with a diatom filter, or using UV light. Algicides can also be used to get rid of suspended algae.
Green spot algae: A small, dark green algae that forms small, round spots on the leaves of plants and the tank
glass. This species thrives in poor and unstable water conditions. Algae eating fish and snails can rid the aquarium
of green spot algae. The stabilization of water conditions helps slow green spot algae growth.
Green bunch algae: This algae forms bunches up to 1.2" (3 cm) long. Green algae is most prevalent in tanks
with excessive lighting and fertilization. Green bunch algae can be removed by hand or algae eating fish.
Blue-green algae: Blue-green algae form a layer that covers plants and gravel. Blue-green
algae are fueled by excessive illumination and high nitrate and phosphate levels. Blue-green algae can produce
toxins that are harmful to fish. Blue green-algae are often refused by algae-eating fish because of its bad taste.
Apple snails can slow blue-green algae growth, but the best treatment is 5-7 days of total darkness combined with
several large water changes.
Beard algae: Beard algae forms long (up to 6"-15 cm), black to dark green, branches
that are introduced with new aquarium plants and are prominent with high nitrate levels and/or carbon dioxide deficiency.
Beard algae firmly attaches to plant leaves, so manual removal is damaging to the plant. Algae-eating fish can
eliminate beard algae as can carbon dioxide fertilization.
Black spot algae: Black spot algae form small, black spots on plant leaves. The cause of black algae is unclear,
but excess nutrients (nitrate) and light help its spread. Control is very difficult, the best means to take is
to remove affected leaves.
Black brush algae: Black brush algae forms dark, muddy-green bunches that adhere leaves, rocks, gravel, and wood.
This red algae causes leaves to die off and thrives in acidic water with a high nutrient load. Short forms can
be removed by algae-eating fish, but long forms are best combated by carbon dioxide fertilization.
Diatoms: Diatoms develop in aquaria that are poorly illuminated, have a high load
of nitrate and phosphate, and a pH above 7. Diatoms forms a brownish layer on plants, rocks, and glass and can
be removed by snails and algae-eaters. Diatoms die off when water conditions improve and lighting intensity is
Algicides are chemicals that can be used to eliminate algal growth in the aquaria. Algicides work on a limited
range of algae including filamentous, blue-green, and diatoms. If possible, seek non-chemical means to combat algae
as many algicides do have side affects towards plants.
Trouble-shooting with Plants
Besides algal infestations, plants can suffer other ailments, especially when the water conditions are not favorable.
Water with incorrect properties can cause as much or more damage to a plant than nutrient deficiency. If plants
begin to wane (i.e. prematurely yellowing and losing leaves, leaf damage), first check that the water conditions
are in order. If they are, see the chart below for help.
-lower leaves on plant stem
-lower leaf loss
||Make sure that the plants have the right illumination period. Change the light bulbs
if they have been used for longer than a year. Make sure that the lights are strong enough for the types of plants
|-small brown spots, developing into holes
|high nitrate content from lack of water changes
||Make a series of moderate water changes.
|-small, irregular holes with sharp edges in otherwise seemingly healthy leaves
||Remove snails by hand.
-premature die off
|carbon dioxide deficiency
||Start fertilizing with carbon fertilization. Decrease aeration.
Recommended Aquatic Plant Resources
Check out the following sites for quality information on aquarium plants: