Re: continous lighting or timed ?

["Tyrone Genade" <Tgenade at akad_sun.ac.za>]

> Jose Perez wrote:
> > 
> > Hi folks,
> > 
> > I am curious to what type of lighting setups people use here. Do you light
> > the tanks for 8 hours, 12 hours or do you leave the lights on 24 hours ?
> > Pros and Cons?

I use fluorescents that span the length of the tank.
I switch them on about 8h00 every morning and put them 
off around 0h00 every night. There is fantastic algae 
growth in the shallow notho tanks but I'm happy with 
that... There is minimal algae growth in the Aphyosemion 
tanks which have a varied assortment of plants.

On 19 Jul 2001, at 12:45, Wright Huntley wrote:

> I once accidentally sterilized a line of guppies by leaving the lights on
> 24/7. I don't do that any more. 

Most animals and plants use day/night signals to reset 
their body clocks. No signal, no resetting... hormonal 
chaos... except with the Ghost crabs which can sit 
months in the dark and still keep regulat day/night body 
rythms...very odd.

> Fish need their biorythms. The change of day length with season is an
> important breeding trigger for some, I think, too. 

Quite correct. You can also fool plants in flowering by 
manipulating day/night length as with fish. Most of the 
triggers are multifactorial though and may have to be 
paraleled with a rise in temp.

> Another argument against constant light is that vascular plants need a dark
> period of respiration (as opposed to photosynthesis) to grow. Simple algae
> do not, and can outcompete the plants for food unless there's a daily
> period.

Not really true... When my brother was too lazy to 
switch his light of for a year we witnessed the most 
fantastic amazon sword and eelgrass growth yet! The J. 
moss and fern also went berserk. As said before though 
the day/night cycles are NB in getting them to reproduce.

*Everyone not interested in plant biochemistry can now 
fade out...*
The dark respiration you talk about refers to 
photosynthetic reactions which can be carried out in the 
dark---the socalled dark reactions. They can and are 
carried out just as effectively in the day. During the 
dark reactions the chemical potential energy generated 
by harvesting light is used to convert CO2 and H+ into 
carbohydrates with ATP and NADPH (an electron carrier). 
The dark and light reactions occur simultaneously in 
plants if adequate light is present. Interestingly, the 
dark reactions require light for maximum rates of carbon 
assimilation.
Needless to say, as a biochemist I've always enjoyed 
plant physiology---plants don't scratch and scream when 
you grind them up into little bits to find out how they 
work.:-)

Bye

Tyrone Genade
Southern African Killifish Society Coastal & Offshore Coordinator
AKA 08248
tyronegenade at yahoo_com
http://www.geocities.com/tyronegenade

Please excuse my spelling.
I'm too lazy to use my spell checker.
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References:

• Re: continous lighting or timed ?
• From: Wright Huntley <huntley1 at home_com>

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