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Didn't think many planted tank folks used metal halides, but 200-500+ are nice numbers. That gives me a ballpark idea of what I've got, just that much closer to dialing it all in! Thanks guys
 

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Good question! From the PAR meter rules:

"What Do My Results Mean?
There is no universally accepted interpretation of PAR values for aquaria. Here are two proposed scales for comparison. All values are given in micromoles per square meter per second.

20-40 low light
40-100 medium light
100+ high light
-or-
40-70 low light
70-150 medium light
150-300 high light
300-600 very high light

By reporting your results and comparing them to others, you can help to develop realistic guidelines for light levels in planted tanks."

From the information we've gathered to date, I tend to agree with the first scale. You can definitely grow low-light plants with less than 40 umol.
Are these numbers at the substrate?
 

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Discussion Starter #83
Most people take these to mean "at the substrate". But really they apply to any place in the tank where you want to grow plants. As we saw at CrownMan's house yesterday, you can have a very lush planted tank with very low PAR values at the substrate.
 

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PAR DATA COLLECTION

Aquarium size: 55 gallon, 48" x 13" x 20"

Type of light fixture: Current USA TrueLumen Pro LED Striplights, 2-48" 8,000k, 1-48"10,000k/actinic blue

Number of lamps, bulbs, or tubes, and wattage: 90 total watts, not going to count the LED nodes

Age of lamps, bulbs, or tubes: 4 days

Distance from light fixture to substrate: 18"

PAR VALUES MEASURED AT WATER LEVEL: 201

PAR VALUES AT MIDDLE: 120

PAR VALUES MEASURED AT SUBSTRATE: 82

Comments: Less than 2 watts per gallon, but I think you can throw that old adage out when it comes to LEDs. I was going to try to go with 2 strips, but I took a strip away from my discus tank and added here when I saw my PAR was 30 with only 2 strips.
 

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I'm not using glass tops and I'm using a Toms surface skimmer to keep the surface clean.

PAR DATA COLLECTION
March 31, 2013

Aquarium size: 72 bow front
48"L 12"W on the ends 18"W at the middle and 24"D

Type of light fixture AND reflector: Finnex Ray 2 DS 48" 7000K LEDs

Number of lamps, bulbs, or tubes, and wattage: 384 LEDs, 39 watts

Age of lamps, bulbs, or tubes: about 4 months old

Other information:

Distance from light fixture to substrate: 22"

PAR VALUES MEASURED AT SUBSTRATE: Directly under fixture, 43 par
6" off from center, 33 par

Comments:
Directly under light
At surface, about 1.5" under light 630 par
6" 200 par
12" 100 par
18" 68 par
22" at substrate 43 par

6" out from the center of the light
At surface 35 par
6" 73 par
12" 77 par
18" 47 par
22" at substrate 33 par
 

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Discussion Starter #87
Thanks to both of you! These are very interesting results, and show that these particular LED fixtures are viable options for planted tanks.

The very different performance of the fixtures may be due to the different Kelvin ratings. High Kelvin has more blue light and this penetrates to a greater depth more easily. We saw the same kind of difference when we compared a 6700 K metal halide and a 10,000 K metal halide at Dallas North Aquarium. The 10,000 K gave lower PAR at the surface, but higher PAR at the substrate.

How do both of you like the appearance of the light?
 

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I really like the color of the Finnex LEDs. My wife does too, and that is the most important.

Here is a link to the manufacture's PAR data, taken through air, for this fixture. My results are pretty close to what they advertise.
 

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Yes, I think I paid $160 something for my 48".

I'm thinking about getting a clamp lamp with the biggest spiral compact fluorescent daylight bulb I can get. Then I will just put that over one of the back corners and put whatever high light loving plants under it. It won't look the best, but I will be able to grow just about anything then.
 

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Posting this as a record trying to figure out why my readings seem pretty high.

Bulbs:
Satco Hygrade (3500K, 2900 lumens each)
KorallenZucht Fiji Purple
Giesemann Midday 6000K
Giesemann Lagoon Blue

Bulb placement in the fixture:
---Satco----
---Midday---
---Lagoon---
---Fiji-----
---Satco----

---Watts------PAR at 18" water depth+1" air-----Bulbs
---24-----------39--------------------------------1x24W Lagoon
---58-----------61--------------------------------2x24W Satco
---58-----------79--------------------------------1x24W Midday + 1x24W Fiji
---72----------118--------------------------------1x24W Midday + 1x24W Lagoon + 1x24W Fiji
---82-----------97--------------------------------2x24W Satco + 1x24W Lagoon
---116---------143--------------------------------2x24W Satco + 1x24W Midday+ 1x24W Fiji
---140---------182--------------------------------2x24W Satco + 1x24W Midday+ 1x24W Fiji + 1x24W Lagoon

Most natural look:
All bulbs - beautiful light, like full sun, all colors pop up (reds blues greens)
2x Satco + 1x Lagoon - second best, very natural looking.

Notes:
PAR measured only in the center of the tank (tank is a 30 gal. Oceanic cube).
Water column is 18".
Air gap between the water surface and the bulbs - 1".
Bulbs have individual Tek reflectors.
Satco cheapo brand bulbs used to ballance the colors.
 

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PAR VALUES MEASURED AT WATER LEVEL: 201

PAR VALUES AT MIDDLE: 120

PAR VALUES MEASURED AT SUBSTRATE: 82
I notice lots of people having reduced PAR deeper in the tank. I measured my PAR and found almost no difference. Done with a Seneye which compared to the Apogee gave almost the same readings.

Some measurements from my 100G:
 

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Discussion Starter #93
Yohan, what type of bulbs are you using? We noticed that lights with high Kelvin did not loose PAR as much from top to bottom of the tank. This is presumably because the blue wave lengths are not absorbed as readily by the water, allowing more light to penetrate to the substrate.
 

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I talked to Hoppy (from whom I got the PAR meter I'm using). So far I think my fixture produces more PAR than any other commercial light. That includes LED.

But there are details about measuring the PAR. The spacing of the bulbs, the tank shape (light reflecting from the glass), the PAR meter sensitivity to wavelengths. That's why I post the primitive diagrams below.

PAR meter sensitivity:
From what I understand so far Hoppy's PAR meter (not the same at the club meter) "...under measures the near UV light, and the near IR light, so the violet bulb (Fiji Purple) may produce more PAR than my meter says it does..". It looks like one needs to know how their meter produces the reading. Bulbs with funky spectrum (like the Fiji Purple or the Lagoon Blue) may actually produce more PAR but the meter doesn't see it very well.

Will the PAR of 2 bulbs be 2 times the PAR of each individual bulb:
Also he says that the PAR of 2 bulbs is expected to be a little less than the sum of the PARs of the 2 bulbs separately. That is due to spacing if I'm not mistaken. But what I see shows that my fixture just adds up the PAR, no loss due to spacing.

I'd be interested to see the PAR of a single Satco bulb compared to two Satco bulbs. Note that in my fixture they are 16" apart. That should lead to not adding up the PAR for the two bulbs. I will post about that later. For now note that the PARs of all the other bulbs add up very well.

PAR and reflectors, spacing, and ballasts:
He says that Tek reflectors are pretty much the best on the market. I use the old style - they are 2" wide (the new ones are 3" wide). That means that the light that hits the bottom of my tank is more directed compared to the new style reflectors. Also the spacing of my bulbs is the tightest possible WITH the best reflectors available. In addition I use Fulham Workhorse ballasts. I understand that many T5HO fixtures have ballasts that underdrive the bulbs. Mine may be driven just right (be as bright as possible without overheating the bulb due to overdriving).

PAR 39:
-----------------
-----------------
=============1x24W Lagoon
-----------------
-----------------

PAR 61:
============= 1x24 Satco
-----------------
-----------------
-----------------
-----------------
=============1x24 Satco

PAR 79:
-----------------
=============1x24W Midday
-----------------
=============1x24W Fiji
-----------------

PAR 143:
=============1x24W Satco
=============1x24W Midday
-----------------
=============1x24W Fiji
=============1x24W Satco

PAR 182:
=============1x24W Satco
=============1x24W Midday
=============1x24W Lagoon
=============1x24W Fiji
=============1x24W Satco

PAR 97:
=============1x24W Satco
-----------------
=============1x24W Lagoon
-----------------
=============1x24W Satco

PAR 118:
-----------------
=============1x24W Midday
=============1x24W Lagoon
=============1x24W Fiji
-----------------
 

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Here's a funny experience everyone needs to hear about:

Today I took the PAR meter to a tank that had 4 year old 220W VHO bulbs. Checked the PAR 6 inches from the bulbs - reading was 45. Checked the PAR at 12" - got a reading of 25.

Then I stuck the meter 10 inches under a 40 watt incandescent bulb that was inside a room lamp with a shade. Reading was 25. Who knows how old that bulbs was.

Basically the 220W of VHO, 10,000K bulbs were so worn that produced as much light as one 40 watt incandescent bulb. That's pretty hard to believe and for some time I thought something was wrong with the PAR meter.

I installed brand new T5HO with Tek reflectors and Fulham Workhorse ballast. Reading 6" under the bulbs was 150.

What I find funny in that is my mentality. I believe it reflects the general mindset of planted tank enthsiasts - to not use common sense. During the last 2 months I had successfully weaned the tank from what amounted to a full blown EI fertilizing, complete with ever present algae. I could not find any other way to keep that tank running without tearing it down (which I could not, the tank is not mine). There were algae present in that tank for years - more or less but always there somewhere. After reducing the ferts substantially and vacuuming diligently 2-3 times only a little BBA on Anubias stayed in the tank. It disappeared when the plants grew well. Funny thing the plants grew better with less ferts! But after a few weeks some plants died off. The others slowed down their growth. BBA returned on the Anubias. I blamed it all on lack of fertilizers. You know - I cleaned the tank and the plants used whatever reserves they had and now they are not growing. That is most of us would think too I believe.

My question is how often do we change our fluorescent bulbs? The petered out VHOs looked bright enough when looking directly at them. But they did zero for the plants. A single new 24W T5HO has a reading of 40 16" below and these old 220W bulbs had 45 just 6" away! From what I can tell a t5HO bulb has a reduced light output after about 6 months. Maybe a little but it is not what was in the beginning. Next time you or someone else asks about algae problems or plant growth problems the age of the bulbs will be one of my first questions.
 

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But what was the PAR of the 220 to begin with? Maybe lots of green, no red or blue? Someone on a Dutch forum stated that Philips t5ho had only 5% reduced PAR over a few years...
 

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But what was the PAR of the 220 to begin with? Maybe lots of green, no red or blue? Someone on a Dutch forum stated that Philips t5ho had only 5% reduced PAR over a few years...
Agreed. Would need to know this to be 100% sure, but even so 45 seems like a very low value for 220w.

I'm curious, have you ever tried using the PAR meter on one of those cheap 250 or 500 watt sodium lights they sell at home depot for night time construction work? I've often heard they don't put out the right type of light for plants but it would be interesting to double check that assumption.
 

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@ Michael: high Kelvin indeed. Lowest are two dennerle daylight bulbs, osram 880 and higher.
 

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I don't know about the PAR when the VHO bulbs where new. But I tell you this - since I own this PAR meter now I take measurements of what not lights (including the bulb under a microwave, ahha). And at close distances the readings are high. Bulbs that look like nothing have PAR that is just fine for an 8-10" deep tank. And to have a reading of 45 with 220W of light is truly amazing - I'm not sure I will find a bulb like that any more.

I have access to quite a few different kind of bulbs - Halides, fluorescents, CF, dome spot lights, LED - and I suspect I will be taking measurements and posting here about them.

A guy that knows more about aquatic plants than most people told me "Any strong light will grow plants well." I have the feeling that might be the simple truth. I'm still trying to make sense of Hoppy's charts of PAR vs. distance from the bulb that he has posted on TPT. According to them a cool and popular LED fixture does not beat 2x24W T5HO. This seems to be the same with virtually all other fixtures on his charts. I'm not hellbent on T5HO being superior but decide for yourself:

DIY T5HO, individual Tek reflectors, Fulham Workhorse ballast - 2x24W, 18 inches from the bulb.
PAR is 79.

Now look for the 18" distance (or to make it easy - the 20" distance). And find a light that produces 80 PAR:

http://www.plantedtank.net/forums/showthread.php?t=184368







Also find the PAR at 18" for LEDs in the link below. None of them gets to 79 at 18". And consider that the LED PAR will be huge right under the emitter but just a few inches to the side will drop dead. The T5 produce that high PAR over a wider area.

http://www.plantedtank.net/forums/showthread.php?t=160396

Don't get me wrong - I am not crazy about T5HO or anything. But what I see is the same old situation - fads and advertisement. About "amazing" lights now.
 

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also ballast will make a difference too. not every ballast is the same. I have always loved fullham work horse 5-7 ballast and tek's reflectors. I use to use the hagen glo reflectors nope don't like them.
 
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