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Thread: Lighting an Aquarium with PAR instead of Watts Reply to Thread
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Topic Review (Newest First)
Today 11:55 AM
Joost Hi,

A friend of mine is interested in using two CFL bulbs above his aquarium. The aquarium holds 54 litres (60 cm length x 30 cm width x 30 cm height). Two IKEA TERTIAL desk lamps will be used to mount the CFL bulbs in a vertical position. The TERTIAL desk lamps have a diameter of +- 16 cm (6,3 inches) and are painted white. The height, from substrate to light source will be approximately 44 cm (17 inches). Pressurized CO2 will be used (up aqua inline atomizer), therefore we're aiming for 35 to 60 micromols/mē/s at the substrate.

According to the chart, when the distance between the substrate and the light source is approximately 17 inches and a 15 watt CFL bulb is used, the CFL will provide about 75 micromols/mē/s at the substrate. Is this correct? This means that even 15 watt CFL bulbs provide too much light.

If the above is correct, should he be using 13 watt, or even less?

I look forward to your response!
01-15-2015 12:05 AM
CowBoYReX @hoppy are you able to answer this?
01-14-2015 01:07 AM
RootedMind Lol, I understand the Kelvin part, really I'm just curious about my PAR readings. I appreciate you responding, though.

Only fools stop searching for knowledge.
01-14-2015 12:11 AM
mef1975
Quote:
Originally Posted by RootedMind View Post
I think maybe I should switch it to: 18, 23, 23, 18, BTW the 18's are 5500k and the 23's are 6500k, any thoughts?

Only fools stop searching for knowledge.
Now, I could totally be wrong, but I think I read somewhere that the K range you ask about is representative of what daylight might be at the Earth's equator, which I guess would be a good thing when it comes to visual light and color rendering, but I don't really know, at all. That K thing confuses me a bit. I think the higher frequency ones have more of a bluish tint, and perhaps, can even penetrate deeper waters better, but as I said, I'm really not sure about all this, I too am an algae grower. lol
01-13-2015 05:00 AM
RootedMind I think maybe I should switch it to: 18, 23, 23, 18, BTW the 18's are 5500k and the 23's are 6500k, any thoughts?

Only fools stop searching for knowledge.
01-13-2015 04:57 AM
RootedMind I'm seeing 70 for the 15w and 115 for the 23w. My tank is 0.55mē, so how would you figure it with 2 of each light in this order: 23, 18, 18, 23? At ~11" apart?
I really wish I had a PAR meter

Only fools stop searching for knowledge.
01-13-2015 04:26 AM
RootedMind That's what I was thinking, my lights are ~11" apart. Also, I believe I read that the smaller diameter of the cone the higher the concentration, so higher PAR

Only fools stop searching for knowledge.
01-13-2015 04:11 AM
mef1975
Quote:
Originally Posted by RootedMind View Post
What kind of PAR readings would you get with an 18w CFL and a 23w both in an 8.5 aluminum cone 18" from the substrate?

Only fools stop searching for knowledge.
Well, I'm pretty new at this, but from I can see in the charts at the beginning of this awesome thread, each light will likely give you something over 50 PAR, but under 100, although, that was a 10" cone, definitely appears to be enough light for CO2, right? Would the PARs be summed together? Maybe only if the lights are close together, would it surely be over 100 PAR?
01-13-2015 01:41 AM
RootedMind What kind of PAR readings would you get with an 18w CFL and a 23w both in an 8.5 aluminum cone 18" from the substrate?

Only fools stop searching for knowledge.
01-12-2015 11:39 PM
jeffkrol
Quote:
Originally Posted by Hoppy View Post
With a lot of effort it should be possible to make a light meter that actually reads in PUR, but I have never seen one, nor have I heard of the existence of one.
I believe PUR is also considered species specific.. so really not worth contemplating much at our "level"... I can think of more reasons not to stress it than reasons to...
01-12-2015 10:27 PM
Hoppy PAR is the light intensity in the 400-700 nm spectral range. PUR is the same thing except adjusted to give more weight to the intensity in the ranges of the spectrum that correspond to that which specific plants use, and less to that in the ranges of the spectrum that specific plants use much less of. You can directly measure PAR, but you have to calculate PUR. So, PUR for a specific light fixture is not readily available, nor easily obtainable. With a lot of effort it should be possible to make a light meter that actually reads in PUR, but I have never seen one, nor have I heard of the existence of one.
01-12-2015 11:27 AM
mef1975 I have a Fish Focus Blue, 13K, 90 degree, from BuildMyLED, which specs indicate a PAR of 60, 24" under the water, 9" from center, where I happen to have a Red Tiger Lotus, so I take it that slowly increasing the CO2 (flourish excel) and ferts (nitrate, potassium, iron) will eventually make the green hair algae go away? How many hours a day should I keep the light on?

Also, am I to understand that one could use an incandescent bulb to dramatically increase the CRI and lux (visual brightness in the tank) without bringing up the PAR and PUR as drastically?

Finally, how does PAR and PUR differ? "Active, "usable", like what does that mean? Would PUR be more accurate when referring to photosynthesis? Why is that not used more than PAR? Or, is PUR like the PAR, but after it goes thru the water column, losing some, and not really applicable in manufacturing specs?
11-25-2014 03:59 PM
nonaldehye no pun intended, I have seen the light--the watts/gal always struck me as utterly bogus---anyone who completed G12 physics knows energy intensity decreases by the inverse square of the distance--- and from this brilliant post, I can see I am growing algae b/c I have a PAR of 50 at the bottom on my 65G freshwater tank... and no co2...either hanging the lights and adding CO2.
Grateful!
11-25-2014 08:05 AM
roadmaster
Quote:
Originally Posted by candymancan View Post
It is a fad but people constantly bash PC lights yet no one cares to measure them if you rely on PAR so much wouldn't it be fair to properly measure PC's and not just T5 lights

Only if your using power compact bulbs.
Mostly reef folks still using these bulbs which I actually quite like.
Anyone who believes PAR is a fad,is doomed from the outset in their effort's at growing healthy plant's.
More likely to experience spectacular algae growth with too much PAR and limited ability to supplement CO2 .
Hardly anynbody's effort's are thwarted by too little light/PAR.
The PAR values of a particular bulb or bulb's,are much more critical than color spectrum.
Most agree on this.
11-24-2014 10:52 PM
candymancan It is a fad but people constantly bash PC lights yet no one cares to measure them if you rely on PAR so much wouldn't it be fair to properly measure PC's and not just T5 lights
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