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-   -   what light level is this (http://www.plantedtank.net/forums/showthread.php?t=216162)

Contrl 01-17-2013 04:16 AM

what light level is this
 
I have a single t12 4foot 40 watt strip light over 2 15 gallon tanks. 12" deep and the light sits 5" above the tanks.

is this low? Medium?..... if I did a double tube t12 or t8 would I be high?


it does grow egeria densa like a weed,,,, but then again that is a weed... :icon_wink

sowNreap 01-17-2013 04:30 PM

Quote:

Originally Posted by Contrl (Post 2265082)
I have a single t12 4foot 40 watt strip light over 2 15 gallon tanks. 12" deep and the light sits 5" above the tanks.

is this low? Medium?..... if I did a double tube t12 or t8 would I be high?


it does grow egeria densa like a weed,,,, but then again that is a weed... :icon_wink

I used my Lux meter on an old 2 bulb T12 fixture with new bulbs done in air not in water. Here's the readings I got:

2 bulb T12 fixture on the 2nd no foil reading I turned the bulb slightly and noticed it got brighter so it's more accurate.
Height Foil Lux/Par --- No Foil Lux/Par -----No Foil Lux/Par
15 -------- 381/50.1 --------- 344/45.3 ------------ 372/49.0
20 -------- 278/36.6 --------- 248/32.6 ------------ 275/36.2
25 -------- 210/27.6 ----------190/25.0 ------------ 202/26.6
30 -------- 164/21.6 ----------145/19.1 ------------ 154/20.3

For background, I was also trying to see if an aluminum foil lined fixture was better than just a regular white painted surface shop light. Comparing the 1st column with the 3rd column appears it's not worth the effort.

I think you can use 1/2 the value to get an guesstimate of what 1 bulb would be. Also, Hoppy says it will get at least 10% more than my data indicates - due to the slight focusing effect of the air to water interface. Unfortunately I didn't do a reading for 10" height and Hoppy didn't chart this fixture but maybe this will help at least a little bit.

This info was originally posted in this thread but I've corrected the PAR values here. In that thread the PAR was NOT based on the corrected conversion number: http://www.plantedtank.net/forums/sh...500&highlight=
I see I need to correct that thread so the PAR values are correct.

Contrl 01-18-2013 02:22 AM

Thank you...

I found a fixture at our Menards that looks perfect, the reflector is mirror shiny... unfortunately they were out of them, the sale ends Sat. If I go back then, and they're still out they did say they'd give me a raincheck, but I do have to wait till the last day.

sowNreap 01-18-2013 05:27 PM

I forgot to mention that there is a chart the for a couple T8 fixtures so you can see how they compare. That post also has a guide to what is considered low, medium or high light. Just in case you didn't see the thread yet it's here: http://www.plantedtank.net/forums/sh...d.php?t=184368

Here's the chart from that post for T8 fixtures:

http://i573.photobucket.com/albums/s...vsDistT8-2.jpg


I can't believe they wouldn't give you a raincheck while you were there instead of making you come back. I usually tell them I can't make it back before the sale ends and never had a store not give me a raincheck that same visit. But at least they will give you one so that's good.


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