Re: [RML] lights and ballasts

Larry Stein (lstein at
Sat, 22 Nov 1997 08:13:24 -0500

This was a pretty intersting article I recently found...

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

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.