Confused about how CFL PAR works
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Old 02-27-2013, 12:17 AM   #1
Jeffww
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Confused about how CFL PAR works


I have a fluval spec V: 10.5"Deep, 6"wide, 16"length.

I'm confused as to how much light a 26W suspended vertically about 4"-5" above the tank would provide.

According to the chart it's over 100+ PAR at the substrate. I have a few questions:

Does this mean nearer the surface where stems are growing the PAR could be nearly 200?
If so is it even possible to provide enough CO2 to the tank without killing all the inhabitants?

Would having two 26W bulbs in seperate reflectors have an additive effect? One lamp doesn't cover the whole tank without leaving some major shadowy regions.

What about 1x 13w CFL? According to the PAR chart this is barely less than the 1x 26w CFL.

Is my best option to suspended it even higher than it already is?
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Old 02-27-2013, 01:36 AM   #2
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Reflector and position of the bulb, horizontal or vertical, etc can affect the par of those bulbs a lot. That's also a 2.5 gal tank, that's only 8" tall, so 4" above there where the data is taken from, which is only 12". Standard height if the bulb was right on top of a 7.5gal cube or 10gal tank. 4-5" above one of those is going to reduce it some.
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Old 02-27-2013, 01:50 AM   #3
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Hoppy's chart has similar conditions to my light and it shows that it's outting 100+ par at the substrate alone. Seems a bit concerning don't you think?
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Old 02-27-2013, 02:21 AM   #4
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Hoppys chart is also a 26W flood light bulb, which is a $60 bulb vs a $3 bulb. Also, what kind of reflector and how is the bulb postioned.
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Old 02-27-2013, 02:54 AM   #5
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It's vertical with in a 8.5" diamter dome reflector. It's a 5000k GE bulb 26w. Similar to the blue line:

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Old 02-27-2013, 02:59 AM   #6
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100 isn't that much if that what you're alluding to.
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Old 02-27-2013, 03:01 AM   #7
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At the distances I'm working with it's around 150-200+ par. That isn't much??
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Old 02-27-2013, 03:04 AM   #8
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If you can keep your CO2 levels high it should be okay. I'm running 125-150 at substrate on my 125g.
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Old 02-27-2013, 03:05 AM   #9
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With your setup you probably want to cover the light to reduce the output.
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Old 02-27-2013, 03:05 AM   #10
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I'm worried about gassing my fish with CO2 running that high. Have you been having problems? Especially in a small tank like this....
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Old 02-27-2013, 03:09 AM   #11
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Well I have a sump and a vortech by the surface so I have a lot of oxygen so it doesn't really pertain to your smaller system.

I agree that you would probably kill everything or end up with algae. I would cover the light to reduce the PAR.
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Old 02-27-2013, 03:21 AM   #12
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What do you guys mean with a good reflector? The CFL bulbs come with various dome lights, some are metal and some are plastic.

If you shine a 23 watt 6500 K at water level with a tank 16.9" L X 10.25" D X 8.75" H, what par would that be?

Last edited by FlyingHellFish; 02-27-2013 at 04:05 AM.. Reason: Copy/Paste error, sorry
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Old 02-27-2013, 03:30 AM   #13
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We're talking about the polished steel dome work lamps you get at a hardware shop for like 5-10 dollars.

Anyways, I'm going to see if I can find some lower wattage daylight bulbs instead (It should help at least a little). I don't want to risk my precious betta to gassing.
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Old 02-28-2013, 01:30 AM   #14
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I run 2x26W over's a shrimp only 20gal with only moss, 2x13w over a 7" cube, 2x13w over a 10gal, 1x13w over a 5.5gal and 3x13w over a 20gal and can grow most plants and have no algae problems and use no CO2.

If you notice in Hoppy's chart, it says 26w CFL GE Flood Light. I don't think he means the normal $3 each bulbs but the $60 flood bulbs, which are way different.

Even if it's the same bulb as your, every tank is different, every water is different, every setup is different. Try it out, if it's too much and you get algae, switch bulbs. If things grow fine, leave it. Yes par from a paricular bulb is a part of it, as are a million other things that two people with the same size bulb and same tank can have one grow plants fine and the other person gets an algae farm. Too many factors. Play around. Experiment. you'll find what works for you.
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