Another lighting question.....

[o0synge0o]

I've always seen the 3-5w/Gal rule when referring to lighting, but have also heard that this doesnt apply when using MH... What do you guys say?

For a 100gal. tank--5x96w PC's would fit well within that range, 2xTrue Actinics, and 3x10k Whites for a total of 480w.(or maybe 3xActinics, and 2x10k's, depending on preference)

100gal. tank, 4x96w PC's-- 2xTrue Actinic and 2x10k's for a total of 384w

Same 100gal. tank--2x175w 10k MH's, and 2x96w True Actinics to total 492w

What would work better, in your opinion.(and for those that are going to ask, it will eventually work up to being a reef tank, one step at a time, so might as well get the lighting correct, right from the beginning, or so I think)

 

[ReefLady]

I've always seen the 3-5w/Gal rule when referring to lighting, but have also heard that this doesnt apply when using MH... What do you guys say?

Well, wpg is wpg, however, this "rule" is to be taken very loosely - and is not really an accurate gauge of lighting. More important is light intensity, and tank depth. MH is far more intense than standard NO (normal output), VHO, or PC lighting, so the same amount of watts will provide more intense/penetrating light.

Same 100gal. tank--2x175w 10k MH's, and 2x96w True Actinics to total 492w

This, IMO, is the best of the scenarios. With MH's, you will have much more flexibility in what types of corals (clams/anemones) you may want to keep down the road. Even though you say "reef tank" there is still a broad range of reef tank types that require different amounts of lighting. Whereas a LPS/softy tank would thrive with 384w of PC lighting on a 100g, if you are even considering some of the highly photosynthetic critters like sps, clams, or anemones, that scenario would not work, and the MH's would be a "must" - IMO.

HTH,

 

[fishfreek]

ANother thing when compairing PC to MH is that PC bulbs emit the same intensity of light thru out their entire lengh of the bulb. For 96W PC's thats 3'. So you get 96W of light over a 3' long area. MH on the other hand are more of a spot light style of bulb where the area directly under the bulb and its imedeate surroundings get alot of the light vs areas a few feet to either side of teh bulb's center.

A single 150W MH would not light a 3' long tank as evenly as a single 96W PC bulb but the intensity would be higher on the MH.

One the setup you described below you have two MH over the tank. Each lighting an area two foot long (assuming the tank is 4' long). The MH on the left side has very little impact on the right side of the tank and the same with the MH on the othe side.