Interesting numbers

Of course PC will always lose out when space or cost of bulb is considered, but that was never the argument I heard when people say PC is outdated. The argument has always been that PC bulbs don't put out the PAR required to keep SPS, anemones or clams.

 

If I was doing fish only you don't need much light. T5 is a good option because bulbs are cheap.. If it was me I would put one MH 150W bulb.. just for the daylight shimmer effect. (and T5 actinic for dusk to dawn simulation) Cheap ebay bulbs too.

 

Only LED's will knock them out of the water for that. There are some florescent's in the comparison but I couldn't tell from the names which are T5 so I didn't use any. I can say this though, the list is arranged by efficiency from best to worst. The MH bulb was only four from the top. The PC bulb was 11 from the top. There are quite a few below that.

 

Well yeah... if you have 4 96W metal halides in a row the water penetration won't be as high as one big 400W bulb.

 

Been trying to find those numbers as well. Can't seem to find any testing as far as water penetration. I do agree though. One point of light putting out the same lumens as four points of light is naturally going to penetrate farther. This only groups T5's with PC bulbs though leaving only there compact size as the leg up.

 

I have PC actinics in my Odyssea hood. I wish I would have went a different route for a few reasons. One is they're expensive vs. the T5 to replace.
Next year I may get rid of the hood and build my own custom lights. I think I'm going to go with VHO actinics since most of the premium tanks in Dallas use those. And I may go SE MH bulbs with the lumen bright reflectors. More bulb choices with SE and the reflectors rock. Much easier to change the bulb.

 

Another thing to put this in perspective. Let say you have a 72" long tank. To keep the comparison even keel you have one 400W bulb vs. 4 96W bulbs in a given area. Both giving similar PAR. You can only put two sets of 96W bulbs in that tank. They're 36" long. You could however add 3 400W MH bulbs.. (or even more if you wish).

 

Here we go. Spectral transmittance of water:

Blue 0.984
Green 0.991
Red 0.944

That is the spectral transmittance per foot through water. This decreases exponentially.

Red:
1ft: .9444
2ft: .9444 * .9444 = .891
3ft.: .9444 * .9444 * .9444 = .842

Now lets compare the 400w MH against 4 96 watt PC. Assuming they have the same light output (as the test showed they were pretty close). The MH would still get 89% of its light through which would be 356 watts. the PC's would get 89% of each 96 watt bulb through totaling about 85 watts per bulb and 341 watts total.

I'm still not seeing an overwhelming argument for MH over PC other than space.


These numbers are based on filtered swimming pool water.

Spectral transmittance numbers are from:
AGi32 Knowledgebase - Transmission of light through water

 

I also agree with the depth comment. This does not factor in depth. This is just straight out the box I assume. Measure a pc at 15" and a halide at 15" and i bet there is much more of a difference. Not to mention at 24"+

Now I have seen many t5's put off the same par values as MH but this was with a lot of them.

T5's have me questioning my lighting choice. I love the shimmer of halides and the intensity, but t5's can highlight some wicked color in your coral.

 

Just read your last post.. Hmm.. waiting for some people to chime in on this one then. VERRRY interesting. We need a par meter