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Re: light intensity
Can another non-expert weigh in here? I think Wayne Jones has
made the most important comment on this subject - that you can't
just flatly state that you can grow any plant, or any bright red plant
(sorry Tom Barr), with 1.5 or 2 watts per gallon, without qualifying
exactly what the lighting conditions are. Tank height and size,
water surface clarity, reflector, ballast, bulb type and age all come
into play. Thus, when Tom says he can grow any red plant in low
light and it ain't da light, I have to ask, what exactly are your low
light conditions? They may truly equal much more than low light.
The rule of thumb about watts/gallon really falls apart at this level.
I will just add my anectodotal comments. There's no doubt in my
mind that light plays SOME part in the reddening of SOME plants.
Hygro polysperma, for example, only develops a reddish tint to the
leaves under strong light. You can dump in all the iron you want but
leaves that are shaded will grow green, and leaves in bright light will
have a pink tint. Ditto the Tropical Sunset variety. Unshaded leaves
are much more vibrant than shaded ones, which generally don't
even show any pink. Same with red Ludwigia repens. I have to
believe that in these cases, it IS the light. Now, for crypts, a
different set of rules seems to apply. But there again I have
purchased crypt plants which were grown under low light and were
totally green, and had them turn deep blood red in my tank with
higher lighting (admittedly there could have been other factors
involved). So perhaps we cannot generalize. SOMETIMES it's the
light.
Just for completeness, here are my tank stats: one tank 30 long @
4 watts/gal (don't cringe, it's a leftover light setup from a reef tank -
and it grows beautiful plants), and one 40 high @ 3 watts/gal. No
reflectors, just white paint. In the latter tank I recently replaced 2
coralife 50/50's (there for color balance with the trichromatics) with
Ultra Tri Lux (a fine bulb!) and the difference in light level is marked.
The plants notice it too. It's still 3 watts/gal, but it means
something entirely different than it did before. I like high-light tanks,
but they certainly do require careful monitoring as things happen
quickly in there.
Cathy Hartland
Middletown, MD