Lighting an Aquarium with PAR instead of Watts

[Troxey]

Another Aquaticlife question. The dual-lamp freshwater fixtures ship with a 6K bulb and a roseate bulb. Would removing the roseate and replacing with another 6K or 10K bulb affect the PAR value either way?

[Hoppy]

Originally Posted by Troxey

Another Aquaticlife question. The dual-lamp freshwater fixtures ship with a 6K bulb and a roseate bulb. Would removing the roseate and replacing with another 6K or 10K bulb affect the PAR value either way?

I don't recall if anyone has reported on the PAR from one of those roseate bulbs or not. Without that information I don't see how we can know.

[Switch]

Originally Posted by Troxey

Another Aquaticlife question. The dual-lamp freshwater fixtures ship with a 6K bulb and a roseate bulb. Would removing the roseate and replacing with another 6K or 10K bulb affect the PAR value either way?

I'm having exactly the same doubts... Specially cause the mixtures of bulbs seems to be less intense then with 2 6k bulbs... On the other hand the roseate is supposed to work on a more appropriate wavelengh for photosynthesis. Would be cool to figure how this balances out... Hoppy!! Can the roseate bulb be less intense to the human eye, compared with a 6k bulb, but have the same strengh in par usable by the plants??

[Hoppy]

Originally Posted by Switch

I'm having exactly the same doubts... Specially cause the mixtures of bulbs seems to be less intense then with 2 6k bulbs... On the other hand the roseate is supposed to work on a more appropriate wavelengh for photosynthesis. Would be cool to figure how this balances out... Hoppy!! Can the roseate bulb be less intense to the human eye, compared with a 6k bulb, but have the same strengh in par usable by the plants??

Assuming the roseate bulb produces a lot more red than the 6500K bulbs, it will look much dimmer, at the same PAR, than the 6500K bulbs. Our eyes are not very sensitive to red light, but very sensitive to green and yellow light.

[Switch]

Hoppy sir!!! Have another question for you... How do u think that surface agitation will influence the effect of par at the bottom of the tank??

[Hoppy]

Originally Posted by Switch

Hoppy sir!!! Have another question for you... How do u think that surface agitation will influence the effect of par at the bottom of the tank??

I haven't yet tested the effect of surface ripple on PAR, but I see no reason why it would have any significant effect. It might even slightly raise the PAR.

[Switch]

Thanks for quick reply!! Can u please elaborate a bit on why u think that?? But dont go too crazy...

[funkman262]

I apologize if this has already been answered, but I'm a little confused by the graphs. Are the Home Depot 2-bulb T8 fixtures really better than most of the 2-bulb T5HO fixtures in the graph above it?

[Hoppy]

Originally Posted by Switch

Thanks for quick reply!! Can u please elaborate a bit on why u think that?? But dont go too crazy...

Light reflects off the water surface in increasing amounts as the angle between the vertical and the light increases - at 0 degrees, straight down into the water, virtually no light is reflected, but at 90 degrees, parallel to the water, or close to it, most of the light is reflected. When the surface is rippled, a lot of the surface is at lower angles to the incident light even way off to the side from the light. So, that might lead to a higher PAR. But, I haven't tested this idea.

[Hoppy]

Originally Posted by funkman262

I apologize if this has already been answered, but I'm a little confused by the graphs. Are the Home Depot 2-bulb T8 fixtures really better than most of the 2-bulb T5HO fixtures in the graph above it?

The chart shows that the diamond plate, 2 bulb, T8, Home Depot shop light gives about 70-75 micromols of PAR at 15 inches. The other chart, of T5 lights, shows only the Hagen Glo, Coralife and FishNeedIt 2 bulb T5HO lights give less than that, and those may have sub-standard ballasts, and do have relatively poor reflectors. I agree that it is hard to believe that the Home Depot T8 light is that good, but someone tested it and that was where the data came from. I also measured the PAR at one distance for one, at a local aquatic plant club meeting, and the reading was consistent with that chart. I saw one on a tank once, and it certainly did look very bright.

[raulfd4]

Two questions:

According to the PAR vs Distance for Various T5 Light Fixtures chart on the first page, the AquaticLife T5HO 36" 4 bulb fixture has about 90 PAR at 25 inches.

Is it safe to assume that the same fixture with 2 bulbs has about 45 PAR at 25 inches?

I have glass covers on top of my tank and they build up quite a bit of condensation.

How much will the glass/condensation on the covers reduce the PAR of a light?

[Hoppy]

Originally Posted by raulfd4

Two questions:

According to the PAR vs Distance for Various T5 Light Fixtures chart on the first page, the AquaticLife T5HO 36" 4 bulb fixture has about 90 PAR at 25 inches.

Is it safe to assume that the same fixture with 2 bulbs has about 45 PAR at 25 inches?

I have glass covers on top of my tank and they build up quite a bit of condensation.

How much will the glass/condensation on the covers reduce the PAR of a light?

That is a safe assumption, that you would get half the PAR with half the number of bulbs.

The condensation on the underside of the cover glass should not appreciably reduce the PAR, but the hard water deposits it may leave behind will reduce the PAR. You need to keep the glass as clean as you can if you want to get the full PAR from the light.

[GDominy]

Originally Posted by Hoppy

Light reflects off the water surface in increasing amounts as the angle between the vertical and the light increases - at 0 degrees, straight down into the water, virtually no light is reflected, but at 90 degrees, parallel to the water, or close to it, most of the light is reflected. When the surface is rippled, a lot of the surface is at lower angles to the incident light even way off to the side from the light. So, that might lead to a higher PAR. But, I haven't tested this idea.

On my former reef tank I actually measured my par using an apogee meter with still water and aggressive surface movement. At a depth of 24" I would measure approximately 350 uMol with still water but during aggressive surface aggitation it would fluctuate between 345-355. From a practical standpoint it averages out and wasn't something I was concerned with.

For reference this was with 108 leds and 16 x 39 watt t5s over a 265 gallon tank. These results may not scale well with less intensity.

[Hoppy]

Originally Posted by GDominy

On my former reef tank I actually measured my par using an apogee meter with still water and aggressive surface movement. At a depth of 24" I would measure approximately 350 uMol with still water but during aggressive surface aggitation it would fluctuate between 345-355. From a practical standpoint it averages out and wasn't something I was concerned with.

For reference this was with 108 leds and 16 x 39 watt t5s over a 265 gallon tank. These results may not scale well with less intensity.

Thank you! That is very good to know. And, it is about what I thought would happen.

[gozzy]

Hi I've been looking at the charts and info on here so first of all thanks for all the good information :-)

I have a Hagen Glo T5HO Lighting and have in there 1 x Dennerle Trocal T5 Longlife Special Plant + 1 Color Plus bulb.

I've only realised after reading this thread they are not HO bulbs but LO (i think) :-(

My tank size is 12" in height and judging by the chart if the light unit is sitting on top of the tank this will give me around 65 par? The chart doesn't say whether these are for HO or NO bulbs though?

Can someone tell me the best use for this fixture in terms of bulbs and height from substrate please? I am looking to be in the high light category.