Description
This article is from the Beginning
Fishkeeping FAQ, by Thomas Narten with numerous contributions
by others.
12 Equipment: Lights & Hood
You will probably want to purchase lights and a hood. A hood prevents
fish from jumping out of the tank and reduces the rate at which water
evaporates. A good hood effectively seals the tank (except perhaps
where the heater and filter reside). You want as little water as
possible evaporating as it may raise the room's humidity to
unacceptable levels and requires more maintenance (i.e., you will have
to ``top off'' the tank once or twice a week to replace the lost
water).
There are two styles of hoods. Full hoods combine the light and hood
as a single unit. Hoods include space for only 1 or 2 (parallel)
fluorescent light tubes, which is fine for fish-only tanks, but not
usually enough for growing plants. Glass ``canopies'' cover the tank
with two strips of glass connected by a plastic hinge, but don't
include lighting. A separate strip (or other) light is used in
conjunction with it. Canopies are a bit better for plant tanks than
full hoods; one can upgrade or change the lighting without replacing
the entire hood, and in situations where very high wattage is needed,
one can usually fit more light bulbs directly above the tank.
Light serves two purposes. It highlights and shows off your fish's
colors and provides (critical) energy for plants (if present).
Unfortunately, the two purposes conflict somewhat. In a fish-only
tank, a single low-wattage fluorescent bulb suffices and does a good
job of showing a fish's true colors (most fish don't like bright
lights either). If you want to grow plants, however, more light is
needed, and the bulb's spectrum becomes an issue; be sure to consult
the lighting sections in the PLANT FAQ before purchasing your light
and hood setup.
Whether or not you will be growing plants, fluorescent lights are the
way to go. Incandescent bulbs give off too much heat, causing your
tank to overheat in the summer. Fluorescent bulbs run cooler and use
less electricity for the same amount of light. Note that in the summer
time, even fluorescent lighting can produce enough heat to lead to
tank overheating problems, if your house gets warm (e.g, you live in
the tropics and don't have air conditioning).
Unfortunately, light grows not only plants, but algae. If your tank
contains lots of the kind of light plants desire, and there are no
plants, algae quickly fills the void. Thus, the ideal lighting for
fish-only tanks differs significantly from that for a plant tank. Two
components of light are of particular importance: intensity (i.e.,
wattage) and spectrum. Plants require intense light and certain
spectral ranges produce more growth than others.
Different types of bulbs give off light in different spectral regions.
So-called ``full-spectrum'' bulbs attempt to reproduce the sun's full
spectral range. They are good both for growing plants and bringing out
a fish's natural colors. Specialized ``plant'' bulbs (e.g., gro-lux,
etc.) emphasize a spectral range that stimulates plant growth. Such
bulbs grow plants (and algae!) well, but fish don't look quite right
under them, because the light does not have the spectrum of normal
sunlight. The common ``cool white'' bulbs give off light designed for
humans in windowless offices; they neither grow plants particularly
well, nor bring out a fish's natural colors. As a quick rule of thumb,
2-4 watts/gallon of full-spectrum (or specialized ``plant'') lighting
is good for plants; for fish-only tanks, use less than 1 watt/gallon,
and avoid using plant bulbs.
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aquaria, fish, acquarium, tank, fishkeeping
