Lighting a Planted Tank

WyldFya

Baryancistrus demantoides
MFK Member
Dec 23, 2005
20,791
64
132
Moscow, ID
By: ErrorS at www.AquariaCentral.com

I want to get rid of watts per gallon, I'm sick of it. It just plain doesn't work anymore.. MHs can be anywhere from 70 to 110 lumens per watt, incandescents and halogens can be from 10-20lumens per watt and Fluorescents (HO, VHO, NO) can be anywhere from 45 to 130 lumens per watt. That's a huge range.. just in commonly used bulbs for aquariums you can go from 70 to 130 lumens per watt.

It's horrible.. I could tell you I had 6WPG of VHOs on my tank, which sounds really really high, but it's only outputting the light of 3WPG of normal output fluorescents.

It's simple enough..

just lumens divided tank (depth*2) + tank width + tank length. It's very simple, based on lumens per gallon except it stresses the tank height more.

In other words.. you multiply the depth times two, then you add this number to the width and length and divide the lumens with it.

So for 10K lumen output on a 55G tank it would be: 21*2 (42).. 42+12+48 (which would be 102), then you divide 10,000 by 102 to get the value you need.

Below 50 is very low lighting - (fish only)
50-150 is low to moderate lighting - (Fish only or lower-light plants)
150-250 is moderate to high lighting - (typical planted tanks without CO2)
250-350 is high to very high lighting - (Good reef tanks or heavily planted)
350-450 is very high to extreme lighting - (the best reef tanks or extremely high light plants)

This is for 10k Lumens, about two 55W power compacts.

72x25x25 - 180G-(tank is 147) - 68
48x24x21 - 75G - (tank is 114) - 87
48x12x21 - 55G - (tank is 102) - 98
30x12x30 - 46G - (tank is 102) - 98
30x12x12 - 20G - (tank is 066) - 155
30x12x18 - 29G - (tank is 078) - 128

As you can see, the 46G, even though it has less volume requires just as much lighting as a 55G.

Now, if it was 20k lumens which is a good value for a 55/75 moderately planted aquarium (This is about two 175W MHs average.. or a bit less than four T5 HOs), you wuold have these numbers.

20K lumens is about what people seem to shoot for in a 20L reef and you can just get by with this amount in a 29G reef.

72x25x25 - 180G-(tank is 147) - 136
48x24x21 - 75G - (tank is 114) - 175
48x12x21 - 55G - (tank is 102) - 196
30x12x30 - 46G - (tank is 102) - 196
30x12x12 - 20G - (tank is 066) - 303
30x12x18 - 29G - (tank is 078) - 256

Most bulbs vary only a small amount in lumen output.. even full spectrum bulbs, for the 5000-6000lumen bulbs (T5 HOs) it's only a matter of 500 or so lumens lost to get some of the invisible spectrums for your plants, which doesn't mess up the values above..

or the equivilent of one 48'' bulb or one of those 40W screw-in CF bulbs, about 3000 lumens.

72x25x25 - 180G-(tank is 147) - 20
48x24x21 - 75G - (tank is 114) - 26
48x12x21 - 55G - (tank is 102) - 29
30x12x30 - 46G - (tank is 102) - 29
30x12x18 - 29G - (tank is 078) - 38
30x12x12 - 20G - (tank is 066) - 45
24x12x12 - 10G - (tank is 060) - 50.. and as you know, one screw in CF is about enough for low light plants in a 10G, most people fit two, which would simply double this number making it 100...
 

WyldFya

Baryancistrus demantoides
MFK Member
Dec 23, 2005
20,791
64
132
Moscow, ID
For clarification, when you see 10K lumens, this refers to 10,000. K standing for kilo or thousands.
 

jcardona1

Feeder Fish
MFK Member
Jun 5, 2007
11,506
37
0
39
South of Heaven
Ok, so we all know the watts per gallon (wpg) rule is pretty much useless these days with all the different types of lighting. there are other ways using lumen calculation but i still dont like this, and is usually pretty damn confusing.

a member on plantedtank.net put together a great chart, using real data gathered with different bulbs and a PAR meter. this is awesome, and is a great reference for seeing what catergory of light youre in when it comes to plants. or how many bulbs you'll need to be in a certain category.

NEWPARVSDIST.jpg

example, let's assume that i have a standard 55g tank(48x15x18). now, with a height of 18", let's say our light fixture will be 18" away from the bottom of the tank after taking into account your substrate depth of approx 2".

so based on this chart, if i were to run one T5HO bulb (assuming the bulb spans the length of the tank), this bulb would give me 65 micromols of PAR, which puts me in the MEDIUM light category. now if my fixture had two T5HO bulbs, just multiply the figure by 2, which gives us 130 micromols of PAR and well exceeds what is considered HIGH light. this may be too much lighting and could potentially give you algae problems. easy enought right??? :D

same scenario, but let's assume we're using a standard T12 bulb. that gives us 10 micromols of PAR per bulb, which isnt even considered low light. we'd need 3-4 bulbs to be in the low light category. wanna be "high" light with T12 bulbs? gonna need at least 8 friggin bulbs!!!

now you see why T5HO are the most effecient and economical choice when it comes to lighting, especially for planted tanks.

so what do you guys think? can we put an end to all those wpg rules? i think this is easy enough, and should be a good guide for those wondering about lighting. afterall, the hardcore planted tank freaks ignored the wpg rule a long time ago!!! :)



here's the original quote, and full thread:

http://www.plantedtank.net/forums/lighting/105774-par-vs-distance-t5-t12-pc.html

I have been wondering how much PAR a typical T12 light produces. Like most everyone else I have just assumed that watts per gallon was a way to guess the light from T12 bulbs, but there is no more reason to expect that to mean anything than there is to expect it to mean anything for other bulb types. So, I decided to do some testing.

I borrowed a new two bulb 48 inch T12 light fixture from one of our local aquatic plant club members, bought a new T12 bulb - a Phillips "Natural Sunshine", 40 watt 5000K, 92 CRI bulb at HD, borrowed our club PAR meter and took some readings. Since I have previously found that I get virtually the same readings with water in the tank and with air in the tank, I omitted the water this time. Then I plotted my smoothed data on a common plot with T5 and PC data:

To compare this with "watts per gallon", I know that a couple of 2 bulb T12 fixtures will grow plants in a 55 gallon tank. That tank is 20 inches deep, so if the substrate thickness is about the same as the height of the bulbs above the top of the tank, each bulb should give about 9 micromols of PAR, or 36 micromols for 4 bulbs. That is right in the middle of the low light range. So my data is consistent with real life results.

The light fixture I borrowed has an acrylic splash shield and a removable back, which is a white reflector. I tested the light with and without the splash shield to find that the shield reduces the intensity about 7%. Testing with and without the white "reflector" shows that the reflector increases the intensity by about 36%. The data used for the chart is with both the shield and the reflector.

Some popular tanks are only 12 inches high. For those tanks T12 bulbs should give about 25 micromols per bulb, so a 2 bulb fixture will give low medium light intensity, probably a good choice for many people with one of those tanks.

I believe T8 bulbs produce about the same amount of light as T12 bulbs, but at a lower wattage, because they are more efficient. The fixture I borrowed uses starters and magnetic ballasts, so I didn't try it with a T8 bulb.
 

pjsmetana

Feeder Fish
MFK Member
Apr 26, 2010
564
0
0
Cocoa Beach, FL
Great... so @ 30" I'm pretty much at "low light" no matter what?
 

jcardona1

Feeder Fish
MFK Member
Jun 5, 2007
11,506
37
0
39
South of Heaven
pjsmetana;4167999;4167999 said:
Great... so @ 30" I'm pretty much at "low light" no matter what?
not really, the data in this chart is when using ONE bulb only. at 30", a T5HO bulb gives you close to 30 micromols of PAR. the highlight category starts at 80, so use three bulbs and youre at 90 (30 x 3) :)
 

Pharaoh

Administrator
Staff member
Administrator
MFK Member
Feb 18, 2008
17,568
171
1,097
Indianapolis
based on this, my four bulb PC light is at roughly 112. I think that's a bit off. I wouldn't dream of being able to run a high light tank of my setup. I could be wrong though.
 

jcardona1

Feeder Fish
MFK Member
Jun 5, 2007
11,506
37
0
39
South of Heaven
Pharaoh;4168949;4168949 said:
based on this, my four bulb PC light is at roughly 112. I think that's a bit off. I wouldn't dream of being able to run a high light tank of my setup. I could be wrong though.
do the bulbs span the whole length of the tank? if so, then the data is correct. the PAR meter doesnt lie. the meter simply measures the intensity of light at the bottom of the tank, regardless of type of bulb, watts, kelvin rating, etc. a good reflector does make a huge difference though...
 

dxdx

Fire Eel
MFK Member
Jan 26, 2010
1,112
4
68
NJ, USA
Maybe I'm missing something - it's late in the workday. But, what wattage is the green line? My 18 watt T5HO bulb produces 100 micromols of PAR at 14 inches?
 

Pharaoh

Administrator
Staff member
Administrator
MFK Member
Feb 18, 2008
17,568
171
1,097
Indianapolis
jcardona1;4169293; said:
do the bulbs span the whole length of the tank? if so, then the data is correct. the PAR meter doesnt lie. the meter simply measures the intensity of light at the bottom of the tank, regardless of type of bulb, watts, kelvin rating, etc. a good reflector does make a huge difference though...
I might have to calculate mine a bit differently as I have four bulbs at 22" each. Two on each side of the aquarium. I'm thinking I should calculate it as two bulbs that run the length of the aquarium.
 

jcardona1

Feeder Fish
MFK Member
Jun 5, 2007
11,506
37
0
39
South of Heaven
dxdx;4267612;4267612 said:
Maybe I'm missing something - it's late in the workday. But, what wattage is the green line? My 18 watt T5HO bulb produces 100 micromols of PAR at 14 inches?
wattage is not really important here. this is measuring light intensity at the bottom of the tank using a PAR meter. so yes, at 14" from the bottom a T5HO bulb gives you approzimately 91 micromols of PAR (didnt look like 100 to me).

it's also important to note that the bulb must span the WHOLE length of the tank, otherwise youll have less light at the edges of the tank. the thing to remember is that height is very important when determining light intensity
 
zoomed.com
hikariusa.com
aqaimports.com
Store