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PAR Data-Spiral Power Saver Bulbs, lighting question

208K views 206 replies 86 participants last post by  jimclassic 
#1 · (Edited by Moderator)
Original title: Hemianthus Callitrichoides and Blysa in 2.5g, lighting question

I am trying to grow these in a 2.5g. My lighting is currently provided by a desk lamp that contains a 5w flourescent bulb that according to package gives off 25w of light.

If you want to see the details, it's THIS ONE.

Is that enough for them or should I get something stronger?
 
#37 ·
That is some really great PAR data for power saver bulbs. I plotted the data on log log paper to see what kind of relationships are there. It looks like the light intensity drops a little faster than if it were just an inverse square drop off. I'm not at all sure why that would be. Also the relationship between intensity and bulb wattage isn't quite linear, with the intensity increasing a bit faster with power than if it were linear. That is understandable because there is more area radiating light with the higher wattage bulbs and less dark area of tube. Also, at equal distances between the light and the sensor, the vertical mounted bulb gives about 55% more intensity than the horizontal mounted bulb. That is probably from less restrike.

The data also has a lot of practical use for guesstimating how many of what wattage bulbs will give a 100 micromol (for example) intensity at the substrate for any given tank size.

Thank you very much for doing this.
 
#40 ·
Cool, I'm glad. That's what I was aiming for. Was quite fun to do. If we all talked in terms of PAR instead of watts, it would eliminate a lot of variables in diagnosing setups. I do wish the meters themselves were cheaper, I know that is the main barrier for hobbyists.

That is some really great PAR data for power saver bulbs.
I also was a little surprised at how useful they could be.

I plotted the data on log log paper to see what kind of relationships are there. It looks like the light intensity drops a little faster than if it were just an inverse square drop off. I'm not at all sure why that would be.
Raising or lowering the reflector over a small tank like that is going to change the light distribution and also reflect off the side glass differently. That divergence from the inverse square relationship basically indicates how the reflector shape and material comes into play. Additionally, the water itself absorbs the light in addition to the inverse square law, no?

Also the relationship between intensity and bulb wattage isn't quite linear, with the intensity increasing a bit faster with power than if it were linear. That is understandable because there is more area radiating light with the higher wattage bulbs and less dark area of tube. Also, at equal distances between the light and the sensor, the vertical mounted bulb gives about 55% more intensity than the horizontal mounted bulb. That is probably from less restrike.
I also think that restrike is a huge factor in limiting the radiating light in the horizontal configuration. But that's what is great about using the PAR meter... if you reconfigure your lighting, you can see in realtime what the effect is going to be in terms of photosynthetic energy for the plants. That 55% increase is not very noticeable to the naked eye, yet it is there.

The data also has a lot of practical use for guesstimating how many of what wattage bulbs will give a 100 micromol (for example) intensity at the substrate for any given tank size.
Yes, a virtual PAR meter of sorts. The thought had crossed my mind... but without accounting for reflector types, light distribution variations, water depth, turbidity, and brand of bulb, you're still back to not knowing exactly how my photosynthetic energy you really have.

Thank you very much for doing this.
You bet.

Any way we could get shots of the reflectors used in your tests? ie: The one for the vertically mounted bulb and the horizontally mounted bulb.
Sure, however, there's not much left to the imagination concerning those two fixtures shown in the diagrams. The metal dish reflector is the exact same material on the inside. The desk lamp is simply painted white on the inside. However, I can photograph the interiors when I get back in town.

I think this is one of the most helpful posts I've read on here. I read it before lights on on my 2.5g tank, that's had somewhat of a halt on the HC growth, and the leaves were starting to get a little pale. I raised the light 1.5" before lights on and it looks nice and green like it should again!
I have no doubt that raising your lights caused a visual difference to you, but the real question is "what was your photosynthetic energy before you raised the fixture, and what was it after?" Such a change in the lighting would take a bit of time to see the results in terms of the growth of your plants - especially with non-co2 - probably on the order of weeks. By raising the light a couple of inches, you are effectively reducing the photosynthetic energy being supplied to the plants... that will, in turn, reduce the demand for nutrients. If there is less demand for nutrients, then your substrate may have a better chance at providing them through normal bio-chemical reactions.

By using this PAR meter, the idea here is to remove the notion of "how much light/watts do I need?" Instead, we focus on how much photosynthetic energy (PAR) is being supplied to the plants. This is not something you can determine just by looking at the setup, or knowing how many watts you have. Maybe you were overdriving the bio-chemical system in your tank, maybe not. A PAR reading would give us a better answer.

If you were already in a good range, then maybe your paling HC is because of a lack of nutrients overall. Do you see how this conversation would be a lot different if you said "I am providing X amount of photosynthetic energy to my plants, but the HC hasn't been doing well." ? Then we could immediately know if your lighting was at fault or not, and then move on to other factors.


yeah I must of not seen that drop checker..lol..I was so focused on checking out those foreground plants...lol, will the tanks by be small...I still love the meaning behind them, it's nice to know something like that is possible
Yes, I understand, totally :)


Cheers all!
 
#43 ·
Those of us fortunate enough to belong to a local aquatic plants group can urge that group to make a group purchase of a PAR meter for all members to use. Then we can do as you say - just measure what we have and make the changes needed to get what we want. Those who aren't that fortunate have to either spend $250 or so on a PAR meter, find someone willing to loan one, made a wild guess, or go by an approximation that gets them close. That is the only value of plotting the data and extrapolating it. Without that, we are stuck on watts per gallon.
 
#49 ·
If that doesn't improve things try to make some mineralized soil.

After seeing people, like Hoppy, whom all of the high tech gadgets I have come to think growing plants is difficult if you have no minerals in the water column.

So how many tanks do you have and what styles are they.
 
#50 ·
Yeah, I dose the water column EI style in all my tanks. The biggest problems I have had is BBA when there is some sort of imbalance. My tanks are:

CO2, 65W PC 20 gallon, with Florabase
CO2, 140 W T5 125 gallon with inert gravel
non-CO2, excel, 28W 15 gallon long with Eco Complete
 
#51 ·
Yeah, I dose the water column EI style in all my tanks. The biggest problems I have had is BBA when there is some sort of imbalance. My tanks are:
How about a picture?

If it gets real bad I found taking the plants out and spraying them with excel helps. Then rinse them in water with conditioner. Also contrary to experienced 1s KNO3 helped it from coming back in my tank. Thus I wonder if you increased dosing if KNO3 if it would balance your tank. Experience 1s say BBA due imbalance of Co2 and per circulation in the tank.
 
#54 ·
I had a lot of jungle Val, which I have mostly culled or given away. Also some Bacopa Carolina. The rest are slow growing plants like the L. Arcuata, the L. Aromatica, Anubias ,etc.

The light is already raised by legs. I think what I need to do is adjust the location of my diffuser, which I am going to experiment with this weekend.
 
#56 ·
Mine don't grow that fast...compared to the jungle Val. I don't like the look of the Anacharis. I just need to prune back the plants enough and change the circulation pattern. The reason for the problems is that we've been renovation the house and we have a second kid coming (in 3 weeks) and I'm changing jobs, so I just haven't had a lot of time to spend on the tanks (I have to move a tank at work home because of that too). I hope to have it under control next month with some serious changes. Thanks for all the suggestions.
 
#60 ·
HI jeremy (i4x4nmore) I am really impressed with your research regarding PAR values. I would just like to know though, most of the people I talk with compare the efficiency of different type of bulbs (in terms of the light it produces against the consumption) in order to have the best lighting in the cheapest electrical bill.
Do you have any research comparing different type of light bulbs using their PAR value against electical consumption so that we may also know which type of bulb is best.

Thanks in advance!
 
#69 · (Edited)
The first chart shows the effect of having the bulb vertical, in a "flood light" type reflector, so that for a 23 watt bulb you can get a good idea about how much PAR you will have at a given distance from the reflector.



The second chart shows the effect of bulb wattage, distance from the reflector, and vertical vs horizontal bulbs. For the three sizes of bulbs shown you can get a good idea about how much PAR you will have at a given distance from the reflector, when the bulb is either horizontal (in a desk lamp type reflector) or vertical (in a flood light type reflector).



The PAR numbers shown are what you should get directly under the bulb, and the PAR will drop off as you move away from being directly under the bulb, except that some light will be reflected from the front and back glass to increase the PAR close to the glass. To get good uniformity of light along the whole length of the tank you would need more than one bulb for any but cube type tanks.
 
#72 ·
Hoppy:

Based on your graph if umol/m^2/s in your post here, am I correct that a single T5HO bulb at about 20 inches from the substrate would be sufficient for my 36" long, 16" tall tank? I have some HC I want to grow up there, which is probably the most demanding species. I tried it, and it just looks so different and dim. Maybe you have to get used to it.

Since the front-to-back distance is only about 12", the light distribution shouldn't be terrible. My reflectors are the cheapo type, though - the NOVA fixture has bent "parabolic" rather than an actual parabola. So that is a minus.

Do you guys think I'm better off running both my bulbs and raising the fixture to something like 24" or running one (or two??) at about 20"?

I am looking for rough estimates here, based on your experience. Thanks a ton. I am an open book here... I don't want to buy into the wpg hype that is so rampant.

Oh, and for reference, I am running pressurized C02 as high as my fish seem okay with (Amano-style) and doing a modified EI dosing schedule to (hopefully) not limit any type of nutrients my plants would need.
 
#73 ·
There are some compelling benefits to using a two bulb or more fixture and suspending that fixture higher over the tank. For one thing, that just about guarantees good uniformity of light all over the substrate. But, even better, it greatly reduces the variation of intensity from substrate level to water surface. And, it allows you to always be able to increase the intensity if you find a good reason to do so. Last, but not least, it gives you more room between the light and the top of the tank to make routine maintenance easier.

About the only disadvantages I see are the extra light spill over on the floor, and the greater power usage. I'm assuming cost of the fixture isn't an issue.
 
#74 · (Edited)
Thanks for the response, Hoppy. I figured you would say that actually. I managed to rig up something using 2x4s that would "extend" my legs about 7-8 inches higher than their default length. It is extremely ugly, but hanging something from the ceiling in my apartment here isn't practical at the moment.

I am very excited to see the results! (or in the case of algae, not see)

Edit: I have some initial results after two full photoperiods. It looks like the stemmed plants are straightening themselves out in an attempt to "reach" for the light. Before they were sortof happy to be bowed over, etc. Using 10 hour photoperiod for now.
 
#75 ·
Thought I should share this ...

Since I don't have the money to afford a PAR meter I did a bit of searching to figure out if there's some cheaper way (and most likely somewhat less accurate way) to figure out PAR readings using a cheaper lux or foot candle meter. Turns out there is. If you can get your hands on a foot candle meter (which is very cheap, ie: $20), here's what you do:

To convert foot candles to lux, multiply the foot candles by 10.764. Then to "roughly" convert from lux to PAR, you need to multiple by one of the following numbers that most closely matches what kind of lighting you are using:

Metal Halide Lamps
AB 150w 6,800 K- 0.02000
Coralife 175w 10,000K - 0.02128
Coralife 175w 20,000K - 0.02128
Coralife 250w 10,000K - 0.01887
Coralife 400w 10,000K - 0.02041
Hamilton 175w "True 10K" - 0.01852
Iwasaki 400w "Daylight" - 0.01754 (using CWA ballast)
Osram 150w 5,600K PowerStar - 0.01818
Radium 400w "Blue" - 0.02083

Fluorescent Lamps
Hamilton Compact Fluorescents (4x55w, 2 Daylight / 2 Actinic Combo)
0.02000
Sylvania PowerCompacts (4x96w, 2 daylight/ 2 actinic combination)
0.01852
URI VHO Fluorescent Lamps (4x110w, 2 daylight / 2 actinic combination)
0.02083

Sun - 0.01812
Incandescent lamp - 0.02041
Cool white - 0.01269
Vita-Lite - 0.01592
Gro-Lux - 0.02702
Gro-Lux Wide Spectrum - 0.01815
HPS - 0.01200
MH Lamp - 0.01342

As you can see there's some decent amount of variation between different light technologies and how much PAR they produce based on their lumen output (or lux which is lumen per area). So obviously this method will give us only a rough estimate of PAR values.

What would make it more accurate though is if people with PAR and lux meters would add to this list of values so that we have more light bulb choices to choose from with exact conversation values.

Hope this helps someone,
Harry

P.S. My sources of info for this were primarily from: http://www.thekrib.com/Plants/Tech/par-moles.html and wikipedia.
 
#76 ·
I can't say whether or not those conversion factors are accurate, but I can say that we will never know the light intensity with any more accuracy than about +/- 10-20%. And, that is being generous. So, assuming those numbers are correct, you can just divide the lux by 50 to get PAR (micromols per square meter per second), no matter what type of lighting you are using.

Always remember that a PAR or lux number has to be associated with a distance from the light, because all light intensity from all sources drops with the square of the distance from the source. This means you can't specify a light as a 100 lux light, for example. It could only be a 100 lux at 10 feet light, which would be a 316 lux at 1 foot light. This also means that you can't accurately say that your tank is lighted at 100 PAR unless you say at what level in the tank that 100 is measured - substrate level, mid tank level, water surface level, substrate at the front glass level, etc.
 
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