>> Question One: Is it true that the intensity of MH is the same as 4
flourescents at the surface
>> of the aquarium?
Assuming that the Metal Halide bulb is 150W and is of the minature type, the
luminous flux on the surface is 11250 lux with a colour temperature of 4200K
over 1m square
For a flourescent tube 36W cool daylight (normal) it is about 2500 lux, so 4
tubes = 10000lux. However, with a flouro system you can vary the colour
temperature ranging from 4000K to 6500K by having one bulb in a particular
temperature (assuming normal bulbs - not the grow-lux, actinic-sun or
So approximately, you will get the same lighting at the SURFACE of the water.
The power consumption is, however, different with the Metal Halide taking about
300W in all (heat, ballast etc) and the flouros - 180W in all (heat, ballast
>> Second Question: If question one is true, does one form of light penetrate
>> than the other? IOW, should a tank that is lit by flourescents be more
intensly lit at the
>> same depth as light from a MH bulb?
The light penetration of a MH with proper reflector can reach up to 36 inches
easily, however, no matter how many fluorescent lamps you have, the maximum
penetration is about 18 inches. Again, if the bulbs are placed at the surface
of the water. This can be easily measured, as you have mentioned, with a lux
>> Does this seem accurate, or does everyone think that I was smoking my
aquatic plants? Could this
>> effect have been caused by the type of reflector or the differences between
A reflector helps immensely. A deep reflector for a MH lamp will increase your
intensity by at least 40-60%. For fluorescent lamps, however, reflectors help
up to 30%. Close proximity of flourescent lamps decrese the intensity because
of adsorbtion effects.