So You Want to Grow Plants in Your Aquarium!
by Rajendra Kumar, G.G.
Originally published in Infoquaria, Aquarist Society of Karnataka, India
Aquarticles
Sooner or later the aquarist gets the urge to create a beautiful underwater planted
garden:
Easy - Buy some attractive plants and stick them in the sand.
Truth - Couple of weeks later all of them have rotted and melted away.
…So what went wrong?
Plants require light, nutrients, trace elements, C02 and substrate to grow.
Let's look at these issues....
Light
A rule of thumb is to provide between 0.5 and 1 watt of fluorescent light
per litre of water in the tank. So for a 2x1x1 tank holding about 50 litres, the minimum
would be 50 x 0.5w = 25 watts, and better still 50 x 1w = 50 watts. Some plant
varieties need more light while others do well even under low light conditions. Do not use
incandescent lamps. These lamps will add unwanted heat to the aquarium which can raise the
temperature to unbearable levels during summer, and they consume a lot of electricity with
low light output. The only advantage is that they are cheaper than fluorescent lamps. With
compact fluorescent lamps becoming cheaper everyday, use them if you can afford them.
These lamps will pay you back in lower electricity bills and lush plant growth. Better
results may be had by using two fluorescent lamps of different colour temperature. Use one
bluish (white) and one yellowish (warm) lamp in a two lamp set up.
Plants need light in the same way as the sun provides daylight. The light must be
switched on in the morning and switched off in the evening. 10-14 hours is the usual
amount. Plants from the tropics need 12 hours even day/night, while plants from
temperate regions are used to short days in winter and long days in summer.
So don't leave your lights on indiscriminately at night. On occasional evenings when
you have guests the light may be left on for few hours extra to "show off" your
aquarium.
Lights may be turned off for a few days to control algae outbreaks. A few days of low
natural light will not do much damage to your plants but will control some types of algae.
Aquatic plants need the same nutrients as garden plants. Fish excretion provides the
macro nutrients N,P,K, i.e. Nitrogen, Phosphate and Potassium. But plants also need iron,
nickel, zinc, boron and traces of many others. These are not easily found by the plants in
an aquarium. In nature most water bodies are very large or are constantly being
replenished as in rivers. Such sources have all the nutrients for the plants. In limited
aquatic environments like the home aquarium some trace nutrients are provided by regular
weekly partial water changes.
Lack of macro nutrients will result in stunted growth, yellowing or even holes in
leaves. These may be caused by very low fish load in the aquarium or too little water
changes. Do not think of adding garden fertilisers, these contain large amounts of
phosphates which will result in algae outbreaks, and excess nitrates will stress your
fish.
It's best to add micro-nutrients only. Pre-formulated micro-nutrient solutions are
available at aquarium shops. Do not overdose, or you may end up killing your fish. Follow
instructions carefully and if in doubt ask a fellow aquatic planter for advice.
Carbon Dioxide (CO2)
Carbon dioxide (CO2) is essential for photosynthesis. CO2 in the water comes from fish
respiration, or is dissolved from the atmosphere. Just as you need to aerate and circulate
water from the lower levels of the aquarium for oxygenation, you need to do the same so
that the plants get enough CO2. The amount of dissolved CO2 is not proportional to the
amount of dissolved 02. These two factors are independent of each other. Proper aeration
and circulation of water will ensure that requirements for both gases are met.
Increased growth of aquatic plants may be realised by injecting CO2 from an external
source. This type of injection provides a method of controlling the pH (acidity) of the
aquarium water and providing the plants with extra CO2 to stimulate growth. CO2 may
be injected from a liquefied source (gas cylinder) or by a small fermentation unit. The
gas cylinder method requires a lot of hardware and is not recommended for a casual
enthusiast. The fermentation method may be easily made as follows:
Take a 1.5 or 2 litre plastic cola bottle, poke a hole in the bottle cap and fix an
airline tubing to it, making sure that this attachment is air tight. Half fill the bottle
with water, and add 1/2 cup of sugar and 1/2 teaspoon of baking yeast. The mixture should
be fermenting within hours. The gas generated during fermentation is fed through the air
line to the aquarium and dissipated through an air stone. This will last about 15 days and
you will need to discard it when the gas output visibly decreases, and mix up a new batch.
Use a non-return valve on the air line to prevent the water from getting sucked back into
the bottle. Do not fill the bottle more than half way, or you may end up with the yeast
and sugar mix overflowing into your aquarium.
Substrate
Aquatic plants need an adequate substrate (sand) in which to root. The substrate should
optimally be 1.5mm. to 3mm. in size. Too fine a substrate will result in anaerobic
conditions for the plant roots - water will not circulate when the substrate becomes
clogged with detritus, and the result is a black stinky mess in which the plants'
roots will rot and die.
The depth of the substrate should be 5 - 10cms. (2 - 4 ins.). Some plants will happily
grow in lesser depths, while others like the Amazon Sword plant need at least 8cms.
of substrate. Its better to make an error on the larger size and have a deeper substrate
where most plants will be happy.
Tips on plants
Select healthy looking plants when buying from local fish shops. Do not buy plants from
aquariums where you can see small bits of plants and leaves floating - these plants are
already disintegrating.
Plants can bring diseases and pests into your aquarium. Sterilise plants by soaking
them for 10 - 12 minutes in a dilute solution of potassium permanganate. The solution must
be light pink in colour.
Before planting, remove all damaged and dead leaves. Don't worry if the old
leaves all die out at first - they will grow back in due course.
Some plants like the cryptocorynes are known to suddenly melt (leaves dissolve into
paste) when the light levels are changed. They will grow back within a couple of weeks.
Some species of aquatic plants change their appearance according to light level and
nutrients available. What is a giant plant in one aquarium will be a midget in another
aquarium.?
The author Raj Kumar is a regular
contributor to Aquarticles. His articles are:
New Aquarium Blues: The Nitrogen Cycle
So You Want to Grow Plants in Your Aquarium!
Substrates for the Home Aquarium
Imaginative ideas for Your Aquarium
Fishy Cartoons (by his daughter, Pia)
There is an article about Raj in the People Section: People/Raj Kumar
Raj runs a Yahoo Group for Indian aquarists, "Aquarists
of India"
Here is a link: http://groups.yahoo.com/group/a-s-k
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