PAR meter & my lights

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fishorama

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Jun 28, 2006
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My plant club has a PAR meter to measure tank lighting. I was surprised my different tanks & lights had similar readings except 1....until 1 of the bulbs burned out. T-5HO x 2 over a 55g (108 total watts); PC over 75g (130w), 2 spiral CFLs over a 20g long but only a 20 inch fixture (26w) also over empty 120g; 1 T-5HO (24w) over 20 long & over an empty 120g long (25 inches tall). All had a PAR of ~15 under the lamp & ~8 at the front, side & under the jungle val. None of the bulbs are new.

I'm sorry I didn't have time to test my garage stash of lights T-8s, T-12s, longer T-5NOs, etc, but when a little sun (high window) came into 1 end of a 20 long, PAR was almost 1000!, no wonder I have algae issues in that tank, lol, even though the sun only hits it for an hour (ish) this time of year. The T-5 HO with 2 bulbs was 23-24 under the lamp, until 1 bulb burned out, then it was 15, so not double, more like 1.5 times. CFL "restrike" didn't make any difference either, nor did legs or no.
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I really thought there would be much more difference with the different tank height & lights. There's a club meet tomorrow, I'll ask about other's results & with LEDs but right now I'm feeling like what the heck, why spend more or update lights? You never know until you test.
 

jpappy789

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Feb 18, 2007
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I'm assuming you're going for low tech? Because 15 PAR is pretty low.

As for LEDs, it varies quite a bit. The fixture I have (current satellite led+) is supposed to be about 36, which is about low-medium based on arbitrary thresholds, at 12". I don't have access to a meter myself, so that's based on others observations.
 

fishorama

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Yeah, no CO2 for me yet & old bulbs but still, until you test, I'm not a believer anymore...LEDs are cool if they're dimmable, I'm more about fish happiness than plants' neediness, lol. I'm not sure yet what my PAR numbers mean in those terms.
 

fishorama

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Oh & I forgot to say my glass tops are dirty, either dusty, mineral deposits &/or algae...except for the 120g, no lid or water at all. I wanted a "real life" PAR reading for what it's worth.
 

fishorama

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Jun 28, 2006
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SF Bay area, CA
So, I guess I need new bulbs! But I feel that PAR testing gave me some valuable insights into my lighting/plant growth issues, there's nothing like testing to know what may be happening in our tanks. All my numbers were from lights to substrate.
 
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