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Topic Review (Newest First)
04-08-2014 01:43 AM
alinam973 im confused i have a 18" 15w GE plant and aquarium on my20g high. how so i tell how many k or lumin it has i don't see it anywhere on the package
10-07-2010 05:33 PM
I might be stupid ?

I dont get this at all !

Ive got 3 40w About 44 inch fluorescent tubes each with there own light spectrum in my 120 gallon tank ie

1 blue
1 white
1 red

will i Calculate it 40watt x 3 divided by 120gal = 1wat per gallon ?

Thats not my real problem i think my light is much more than that since I have more area of Light?
08-31-2010 10:12 PM
forddna Okay thanks Hoppy!
08-31-2010 09:14 PM
DarkCobra Found this today, and thought it might be worth sharing as a graphic representation of what's already been said:

Originally found at

Note that:

1) This describes only lumens (brightness as seen by the human eye) produced in all directions.
2) It doesn't address PAR (brightness as "seen" by plants), although lumens and PAR are at least loosely correlated in most cases.
3) It doesn't address reflectors. Lights typically radiate in all directions, and we need to redirect that into a narrow beam. Some light is inevitably lost in the process. Lights like linear T5's end up being more efficient in aquarium use because they have shaped and mirrored reflectors available which lose little light. Other lights are harder to design efficient reflectors for. LEDs are a unique case, they don't need reflectors since they already radiate in a narrow beam; so no light is lost at all.
4) I'm not sure how old this chart is, so it may not represent recent advances in LED lighting. LED efficiency continues to improve. Efficiencies as high as 135 lumens/watt have been reached for white LEDs in the lab, as documented here; which meets or exceeds the efficiency of all other lighting types even before considering the advantage of LEDs not needing reflectors. We'll probably all be using LEDs in 10-20 years.
08-31-2010 07:47 PM
Originally Posted by forddna View Post
The 36w reflectors from AH, if I'm not mistaken, are 22" and the bulb is 18". So how do you think that would compare with a 24" 24w T5HO with a 24" reflector?
The bulbs are 16.5 inches long. As I said above, you would get about 70% of the PAR that a single T5HO bulb would give, and the T5HO would be 24 inches long, so it would cover the whole substrate better. I use one of the 36 watt AHS kits over a 15H tank, which is 20 inches long. I get about 30 micromols of PAR with the light 23 inches from the substrate, and it is uniform over the entire substrate. If the light were 16 inches from the substrate I would get about 70 micromols. If the tank were 24 inches long, the intensity might drop a little at the ends of the tank, but not by much, with the light 23 inches high. It would drop more with it at 16 inches, however, if you keep the inside and outside of the glass sides and ends of the tank very clean, you get much better uniformity because of reflection off the glass.
08-31-2010 07:10 PM
forddna The 36w reflectors from AH, if I'm not mistaken, are 22" and the bulb is 18". So how do you think that would compare with a 24" 24w T5HO with a 24" reflector?
08-31-2010 06:33 PM
forddna I'm comparing AH Supply individual reflector 36w PCs to comparable individual reflector T5s. I can only use retrofit kits inside my canopy.
08-31-2010 04:13 PM
Originally Posted by forddna View Post
I'm not very good at understanding lighting, even with the info provided. It just doesn't click for me.

Can someone tell me how 24w of T5 would compare to 36w of PC?
A 24 watt T5HO is about 24 inches long, so it can cover a 24 inch tank very well. A 36 watt PC is about 17 inches long, so it leaves the ends of a 24 inch tank darker than the middle.

The reflector is a very critical part of any light fixture. T5HO fixtures almost always have excellent, highly polished aluminum reflectors, so most of the light the bulb produces actually reaches the aquarium. PC fixtures, other than AH Supply, tend to have much poorer reflectors, so less of their light gets to the aquarium. On a 16 inch high tank, the typical T5HO, single bulb fixture should give you about 100 micromols of PAR - high light - while an AH Supply light should give you about 70 micromols of light - medium light - and many PC fixtures would give you about 30-40 micromols of light - low light.
08-31-2010 02:24 AM
forddna I'm not very good at understanding lighting, even with the info provided. It just doesn't click for me.

Can someone tell me how 24w of T5 would compare to 36w of PC?
08-26-2010 01:30 AM
eNdoubleU Thanks Hoppy, I was reading that post after I posted here. It was a really good and very informative read. I am going to use verticals and by your suggestion 3x 6500K. I have also read up on the spacing and I wish I could afford a PAR meter. But I may be able to get my hands on one and fine tune it. Thanks.
08-26-2010 12:58 AM
Hoppy Read this thread: From that you can figure out how many of what wattage spiral fluorescent bulbs you would need, with them mounted either horizontally or vertically. You would need a lot of bulbs if they are horizontal, or a lot less if they are vertical. You can't make the decision by adding up the wattages.

If you are willing to use Home Depot work lights, and 26 watt 6500K bulbs, 3 of them will be adequate.
08-26-2010 12:41 AM

Hi, I'm new to the forums and read this entire thread and the links that were available. A few of the links posted are not working, btw =[

So, I just started a 29g tall tank, meaning 18" high. My tank came with a 20W 18,000K, I know too high =[ and I'm looking for a budget solution for lighting for plants. According to research on my plants, I need med-high lights.
I'm thinking of making a hood out of wood from home depot, then buying reflectors and using 4 spiral 27W 6500K bulbs. Is this right? According to the article by Erik Olsen, I need about 93W of lighting.

In case I'm wrong, the plants I want in there are echinodorus amazonicus, argentinensis, cordifolicus, and tellenus. Thanks.
08-25-2010 07:41 AM
James A Hi..!!
The lumen and the watt are both units of measurement. The lumen is a measure of light while the watt is a measure of power.
04-20-2010 04:02 AM
edger I have this light:[/URL]

it lists these properties:

• Wattage: 27 watts
• Incandescent equivalent: 125 watts
• Dimensions: 5.75" x 3.25"
• Light Output: 1,860 lumens
• Color Temperature: 6,500 Kelvin

This is all on a 6 gallon Fluval Edge. Do I have enough or do I have way too much for this tank. I keep reading that if I have too much, I am asking for an algae bloom.

03-10-2010 12:07 PM
Ennio I would like to add that the webpage referred to a few posts back is very wrong when LED is concerned. The lumen-requirements stated there are based on non-directional sources. LED is extremely directionally focussed (usually beaming 120 degrees or less). Meaning the lumen reaching an aquarium bottom surface would be much much lower than the requirements stated on that page, yet would be more than enough for plants and the human eye.

With LED there is no loss at the back (top of aquarium) or sides, so you need no reflectors either. It is also noticeable that the light from LED does not reach out of the sides of the tank, as other lighting does.
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