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Color temperature vs. Lumen Output

Hello all,

I am in a quandary about which kind of metal halide bulbs to purchase and 
thought that I would turn to the experts on this list for advice.  I have 
benefited greatly from the collective wisdom of this list without being 
able to add much useful information myself - I am grateful for the 
education.  To the point.

I have a 90 gallon plant tank with UGH, Dupla Laterite, CO2 injection, 
Canister Filter, recently started PMDD additions.  It is an open top 
lightly stocked community tank that currently has 2 - 175 Watt Metal Halide 
bulbs (CRI 65, 4000K, Medium Base) in fixtures that I made myself.  Growth 
is good but I have an algae problem since I don't have the PMDD dosing 
correct yet.  The bulbs that I currently have are old and noticeably dimmer 
than when I got them.  It is time to buy new bulbs and my choices are as 

175 Watt, 4000 K, 65 CRI
100 Watt, 5200 K, 75 CRI

I am limited to these choices because I used the medium base in my 
fixtures.  The Mogul base would not fit in the housings that I used.  Other 
bulbs, i.e. 175W 5200K do not seem to be available in medium base.  My 
question is this--would it be better to go with 200W total of 5200K light 
or 350W total of 4000K light?

I would appreciate your opinions.


Jamie Howton
Operations Manager
Fotofabrication Corp.
Chicago, IL USA
Tel:  (773)463-6211
Fax: (773)463-3387