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Light Intensity, Spectrum and Hard Water
>Even my famous red horemanii
>looses the dramatic red color and coverts to a pleasant but greener
>apprearance (people who have visited my place need to comment because I am
I will attest to the amazing color of this plant. The leaves range from a
dark garnet red on the newest leaves, to maroon so dark it's almost black
on the mature leaves. I have a piece of this plant in one of my tanks, and
have not been able to get it to come close to the color it has in Neil's tank.
>For a given mix of bulbs, more intensity "may" be needed in some aquariums,
>say with harder water. Some gardeners like Karen Randall claim that they
>need at least more 50% more light than me to grow some plants as well.
>Apparently, this phenomenon is also the reason that hard water requires
>higher concentrations of nutrients. Karen: please comment if our
>comparison of wattage considered the red spectrum (and blue) that my lights
I haven't commented till now because I really don't have a lot to add to
the lighting part of the discussion... I agree with what both you and
George have written. I think it's pretty well established that you can
have good growth quantitatively with any sufficiently intense light source.
I also agree that there have not been any studies that I am aware of that
look at qualitative growth (color, leaf shape, flowering etc.) in response
to different wave lengths of light.
While I haven't directly compared the spectral curve of your lights and
mine, I do know that mine are full spectrum tri-phosphor bulbs, with good
coverage in both the red and blue parts of the spectrum.
As far as whether it is the hardness of my water or some other toxicity or
nutrient blockage problem I can't say for certain. Certainly by European
standards, my water is not very hard, (GH and KH both @ 5) but it is much
harder (and probably contains more impurities) than either yours or
George's. I get good growth, (in everything but that danged soil substrate
tank ;-) and can grow a good many species, but only by pumping in more
light, more CO2 and more nutrients than you do. I haven't compared
directly with George, so I don't know how much CO2 or trace element
supplementation he does, but I don't believe he ever adds N, and I need to
fairly regularly. I do remember discussing with Claus Christensen that
tanks with harder water, in general need higher levels of trace element
There are some species I cannot grow in my tap water, but I've had no
problem with these plants using the same methods I use in all other tanks,
and substituting either bottled water or a rainwater/tap water mix. (too
cheap and too lazy for DI or RO) This is true not only in the house with
artificial light sources, but also in my tub ponds outdoors in full (8-9