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There is lots of good stuff available on the web about lighting
systems. Over the past year I reviewed it all, and, pretty
much as a newbie, built a couple of lighting systems. Here is
some thoughts I hope will help some other newbie who is
wading thru the lighting information.
I have a 55 gallon aquarium with four 40 watt florescent
lights (397 watts per square meter) and a 120 gallon
aquarium with four 110 watt florescent lights (592
watts per square meter). The behaviour of the same species
in the two tanks (water quality and fertilization being pretty
much the same) is TOTALLY different. Plants grow well
in both tanks, but under the lower light the plants all shoot
for the surface as fast as possible and tend to lose their
lower leaves, looking rangy. Under more intense light
the leaves are generally smaller, the plants spread out in
mid-water instead of shooting for the surface, and they keep
their leaves all the way to the bottom.
Also, the plants show more purple and red under the intense
light, while the same plants in the 55 are all green. Green is
nice, but some red and purple make a prettier tank. I have a
book that says there is rumored to be a subspecies of
hygrophila polysperma that has purple leaves. Don't believe
it. Regular old h. polysperma will show beautiful color if
given enough light.
The research I did led me to believe that intensity of light
was most important and that color spectrum was not very
important. Since the intense lighting on the market is all
aimed at reef-keepers, I ended up with a reef system that
had two daylight trichromatics and two actinic blues. The
strong blue spectrum wasn't very warm to look at, but the
plants seemed fine at first. The reds and purples that you
see under strong light were VERY strong. I had some
hygrophila difformis that looked like decorative kale. This
was a very pretty effect, but I began to notice that the rotala
wasn't just red, it was turning brown. I replaced the two
actinic blues with daylight bulbs and my problems disappeared.
The leaves of the h. difformis went back to bright green,
although the stems are still red. The rotala went back to
red and started growing again. In general things got greener,
but still with plenty of red and purple accents.
Bottom line is that spectrum does matter at least this much.
The reef-keeping lights are just too blue for freshwater