best lighting photo period

I am getting ready to set up the lighting on my newly set up 125. I am going to
use metal halides because I have many emergent plants. Although I have been
doing this for a long time I am alwasy looking for advice from those that are
more in the know than me. So here is the situation. 125 gallon home made tank.
surface area of 60 inches by 24 inches 2" of peat moss mixed with volcanic rock
dust and a very small amount of mushroom compost covered by 4" of builders sand
with fiberglass screen seperating them. For the last few months the tank has
been lighted by florescents but now that is turning warm the emergent plants
are starting to grow and as they break free of the surface I am going to need
more light. I am trying to decide between two 175 watt pendants and a 1000 watt
pendant that moves back and forth across the tank every 10 minutes or so. I
have used both with good results in salt water but now I am going to use them
to grow dwarf cattails, dwarf umbrella palms, water irises, cypress tress,
water tupelo trees, and mangrove trees. Along with lots of floating plants and
submersed plants. My question is what is the best lighting cycle? If I use the
1000 watt it will only be lighted for 4 to 6 hours with florescents coming on
before and going out after the metal halide goes off. Is 12 hours the best way
to go or should the light cycle be shorter or longer? I have experimented with
this in the past but I would like the input of some of you who have also tried
different photo periods. I have a friend that has a scanner so I will be able
to post the photos of this tank to anyone who is interested.

Moon
remove nospam from e-mail to send to me, I grow trees in aquariums like bonsai.
I breed dwarf crayfish, great for planted community tanks. If you can get me a
shovelnose sturgeon fingerling (Scaphirhynchus platorynchus) no wild caught
please, contact me