New LUX meter

DelawareJim · Post by **DelawareJim** » Thu Jan 04, 2007 1:33 pm

I've been playing with my new LUX meter I got on Tuesday for Christmas and have some amazing observations.

I always thought my 110 was under lit even though it has 2-175 watt MH and 2-40 watt flourescents (3.9 watts/gal)

With the sensor resting on the center cross brace, 3" below the fixture - 6,360 LUX
With the sensor 1" below the surface - 5,000 LUX
With the sensor 12" below the surface - 1,200 LUX
With the sensor 26" below the surface (resting on the gravel) - 450 LUX.

No wonder I can't grow stems in this tank!

My 29 gal Endler's tank with 1-65 watt, 6,700K CF (2.24 WPG)
fixture 15" above the sensor (off the tank) - 2,300 LUX
With sensor 15" below surface no cover - 2,100 LUX
With sensor 15" below the surface with glass cover - 2,000 LUX

Can't explain why the CF has a higher LUX reading even though it's 3" deeper, other than it's a newer bulb.

Natural sunlight through double pane window - 21,600 LUX.

Interesting to say the least.

Cheers.
Jim

fredyk · Post by **fredyk** » Thu Jan 04, 2007 1:53 pm

yes very interesting. My fantasy tank is a 120 gal with MH lighting, so's I can grow cool stems and have nice carpeting. Hmm...computing a new fantasy tank..

Mark

Ghazanfar Ghori · Post by **Ghazanfar Ghori** » Thu Jan 04, 2007 2:10 pm

With MH the wattage you need to use depends on the depth of the tank
in order to punch through the water column.
Other factors:
The age of the bulbs.
How high the light is above the water surface.
Water clarity.

With a 26" water column - you should consider 250 watters.

Post by **krisw** » Thu Jan 04, 2007 2:14 pm

I'm not sure I'm following your comparision. To do an accurage comparison, shouldn't you measure the MH lights at 15" below the surface, and compare that number to CF measurements at 15" below surface?

Also, is it possible that your reflector on your CF reflector is more directed, where you MH is dispersing light outward circularly the further away from the fixture? (that's my idiot guess)

Jeff120 · Post by **Jeff120** » Thu Jan 04, 2007 2:14 pm

OHHHHH, sounds like a fun toy to bring to meetings!

Post by **krisw** » Thu Jan 04, 2007 2:30 pm

OHHHHH, sounds like a fun toy to bring to meetings!

You're just hoping it would go off the scales when you walked into the room, aren't you?

DelawareJim · Post by **DelawareJim** » Thu Jan 04, 2007 2:32 pm

Ghazanfar; yes you're right on all those factors and I have been considering 250's for over a year. This helps justify it with the boss

The bulbs are old, and the surface has a lot more rippling from the filter outlets vs. virtually none on the 29 gal, so that accounts for some I know.

I just kind of chuckle now when I think of my posts on APC where I argured my tank was under lit since the few stems I did try always performed better as they neared the surface if I could get them to live past the first 6" from the bottom and all the replies I got was that at 3.9 WPG I had more than enough light.

And yes Kris you're right that the MH light should have actually been measured at 15" too. But I was a bit lazy and held the sensor in the flat of my hand with the inside of my elbow resting on the rim of the tank in the 110 (about a 12" reach this way) vs. letting the sensor rest on the bottom at 15" in the 29 gal.

Jeff; I've been thinking of bring it to meetings so we can compare notes. Should be interesting when we have different fixtures on similar tanks like 29's.

Cheers.
Jim

Post by **krisw** » Thu Jan 04, 2007 2:45 pm

Should be interesting when we have different fixtures on similar tanks like 29's.

Yeah, I'd be interested to see the difference between the new hyped T5 strips verses old-standby AHSupply PC kits.

New LUX meter

New LUX meter

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