PAR meter readings

I just borrowed an Apogee Quantum PAR meter to do some testing on my lights. I currently run 3 175w Iwasaki 15K metal halides in my DIY Lumenarc Mini reflectors. My plan is to take a reading out of the water about 6" below the bulb, 1 right below the surface, 1 about 1/2 way down (12" or so) and 1 at the bottom.
I also have some old 175w MH bulbs (used aprox 18 months) I'm going to test. I have XM 10K, XM 15K, Hamilton 14K, Ebay 14K $10 cheapos and maybe a Coralife 5K and Coralife 6500K....if I can find them and didn't toss them out.
Anyone have any suggestions or ideas for the test? My cousin has T5's on her tank. I don't know how old her bulbs are or if she will be around for me to test them, but that's the only access I have to T5's. I can test my VHO SuperActinics, but I don't know if that's even worth doing.

if you can test some t5's that would be great. and i am also intrested in the par for the halmition 14k mh

Sounds like you've about got it covered Capt.
Though I'd be interested to see where 250 watt Phonix 14000K bulbs would read if you got access to any.

I'll get to those, but the #'s won't be good....at least compared to the Iwasaki's. I never tested them, but being I used them for years, I would guess the Hamilton's and XM 15k's will be real close and the Ebay's will be lowest.
I have 250w ballasts, but no bulbs. I would expect, going by the #'s on Sanjay's site, the Phoenix 250w 14K DE's would be very similar to the 175w Iwasaki 15k's. I was going to use the 2 250w ballasts I have, but Sanjay talked me into staying with the Iwasaki's.


This isn't going to be quite as simple as I though. It's not easy finding open areas to hold the probe without getting burned by the other lights or accidentally fragging a few corals. I have it mounted to a piece of 1/2" pvc with a 45 on the end so my arm won't cast a shadow on the probe. I have alot of surface movement, so that has an affect too. I might check with the pumps on and off, but this is sounding like a weekend project...lol.

Here's s few quick #'s. The bulb is about 12" above the water.
Iwasaki 15K - 12 months old
6" below bulb out of water - 1575
1" below surface - 625
12" below surface - 325
bottom - 200

XM 10K - aprox 12 months old
6" below bulb out of water - 1630
1" below surface - 615
12" below surface - 275
bottom - 180

160w VHO SuperActinic - 12 months old
about 1/4" under bulb - 345. If I go lower, the # get higher because the probe starts picking up the other light.

I never thought that clear water would drop the PAR that much in just a few inches.

Capt ant chance of testing either 250w or 400w Radiums? I switched to them a few months ago and dont really care for the look if you gave me some PAR numbers to also dislike that would give me enough reason to switch them

Ryan, I do have a 400w ballast, but no bulbs. The guy I borrowed the meter from runs 250w Radiums on his 180. He used to run the Iwasaki's, but wanted more blue. He said the Radiums test close (a few points higher) to the Iwasaki's. He switched for the color tho, not for more PAR. He said he saw no difference in growth.
I have 2 250w ballasts and I was going to use them. I talked to Sanjay for advise on what bulbs to use and he told me to stick with the Iwasaki's because they have the PAR of most 250's, but only use 175w. He told me the only thing I would gain was a bigger electric bill going to 250w. Keep in mind this is for my 125, which isn't as deep as a 180.

Here's the results from 6 different bulbs I tested. Not suprising is the #'s pretty much match the Performance Data from Sanjay's lighting site.
All these pics were taken with the MH lighting only and my camera set to manual so nothing changed for the pics except the light.

Iwasaki 15K

6" below bulb out of water - 1575
1" below surface - 625
12" below surface - 325
bottom - 200

XM 10K

6" below bulb out of water - 1630
1" below surface - 615
12" below surface - 275
bottom - 180

Coralife 5500K

6" below bulb out of water - 650
1" below surface - 310
12" below surface - 155
bottom - 110

XM15K

6" below bulb out of water - 500
1" below surface - 225
12" below surface - 110
bottom - 80

Ebay 14K

6" below bulb out of water - 470
1" below surface - 230
12" below surface - 115
bottom - 95

Hamilton 14K

6" below bulb out of water - 450
1" below surface - 205
12" below surface - 95
bottom - 85

for sure, water is a killer on par readings... it's insane. I think we all lose track of the fact that even MH lighting is pretty weak when you're talking water penetration.

Consider this, even at the equator, with the sun directly over head, 0 photosynthesis is able to occur below about 250-300 feet. Makes you realize how shallow high light SPS must be, even in the ocean :P

This makes it easier to compare.