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Re: red light

Pete Mohan said....

>The latest discussion of spectrum vs. intensity brings up an issue that has
>been puzzling me.  My first plant tanks were lit entirely with incandescent
>floods, because that's what I had available.  I had terrible algae problems
>but my Rotalas were deep red.  I replaced the floods with a 175 watt, 5500K
>metal halide when I set up a larger (70 gallon) tank, and the Rotalas now
>refuse to redden even tip near the surface in the portion of the tank directly
>under the MH.  Oddly, the red melon sword I recently bought is reddening as
>expected. Has anyone discovered that red emmisions are critical for color
>production in certain plants?  I would expect that anyone using JUST mercury
>vapor lamps or 6500K fluorescents might have encountered this phenomenum, if
>it exists. 

In my 30 gallon both Rotala macrandra and Rotala indica redden under the
5200K MH 175. Maybe you need more light.

Dave Whittaker
ac554 at FreeNet_Carleton.ca