52 Lighting
Description
This article is from the Aquaria: Plants FAQ, by multiple authors.
52 Lighting
contributed by Dennis Bednarek and Hardjono Harjadi
All plants have a cycle in which during the light hours they use CO2
and release Oxygen through a process called photosynthesis. During the
dark hours the opposite occurs and the plants use Oxygen and release
CO2 in a process referred to as respiration. In most aquarium plants
the period of photosynthesis in nature is between 10 and 12 hours
which should be duplicated as closely as possible in the aquarium to
allow a balance between the two processes.
In nature some plants are located in large open ponds and receive a
large quantity of light, others are located in triple canopy jungles
and receive low quantities of light. Each variety of plant has its own
light requirements and for best aquarium results these requirements
should be met as much as possible. In this FAQ we will divide the
plants into groupings that require low light, low to moderate light,
moderate to bright light, and bright light. There are also bog plants
that are often sold as aquarium plants which we shall not cover in
this FAQ except to mention here that their lighting requirements are
usually greater than even the bright grouping.
Fluorescent lighting is the most economical means of establishing a
broad spectrum of light in an adequate quantity for the survival of
aquatic plants. It is recommended that broad spectrum tubes be used to
produce the proper lighting similar to the varieties sold in plant
stores and aquarium stores, rather than the standard cool white bulbs
available at hardware stores. People have had good luck with almost
any of the "full spectrum" or plant specific bulbs (Vita-Lite, GE
Chroma 50 and 75, Phillips Agro-Lite, UltraLume and Advantage X). The
more expensive "three phosphor" bulbs like Triton and Penn-Plax
Ultra-TriLux seem to have a more realistic color rendition. You can
combine different types of bulbs to achieve the same results but the
tri-phosphor bulbs are generally much brighter than less expensive
types. Note that fluorescent bulbs age and will lose intensity over
time. It is recommended that bulbs be changed every 6-12 months (try
to have the bulbs on a rotating schedule, i.e., a new bulb every 3
months rather than 2 new bulbs every 6 months).
When calculating the amount of lighting you will need there is a
general of thumb. First multiply the surface area of the aquarium by
the distance from the light source to the top of the gravel. Then
depending on the type of plants you desire multiply this by one of the
factors given below.
Low light plants 0.08
Low to Moderate light plants 0.12
Moderate to Bright light plants 0.18
Bright light plants 0.27
This will give you the ideal watt hours of fluorescent lighting that
you need. Divide this number by 11 and you now have the approximate
total wattage of lights you need. Unfortunately this number may not be
equal to what is available in bulbs so find the combination of wattage
that will most closely match this requirement and adjust the available
time to match the watt hour calculation.
Example: required watt hours is 1440, divided by 11, is 131 watts of
power. since the closest is 3, 40 watt tubes we divide 1440, by the
120 watt total and we find we need 12 hours of lighting at this level.
Warning: A common mistake is to deviate greatly from the 11 hours of
light to compensate for low or high wattage. If the light time exceeds
16 hours more wattage should be added to reduce this time, Or if the
light time is less than 8 hours less wattage must be used to allow
adequate time for photosynthesis.
When selecting plants also keep in mind that large center plants will
shade the smaller plants under them and that higher light requiring
plants should not be selected for small filler plants.
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