Watts Vs Lumens

[Piscator]

I am working on a Biotope tank setup for a flooded Amazon stream and the plants for such a biotope all require bright light (Cabomba, Amazon Swords, Helzine, Milfoil, etc...). The tank will be 75 US gallons (285 liters) and the height is 20 inches. I will mostly have Angelfish in the tank.

The gent at my LFS was telling me that for this setup I would need 3-4 watts/gallon. But... he then says to me that this is not really the case because it's the "Lumens" of the light source that really matter the most. Seems logical to me because watts is just a measurement of power being used, and not of actual light intensity. He also tells me that 1 Watt = 680 Lumens (at human eye sensitivity of 555 nanometers). So... this somewhat translates to 2,000-2,700 lumens per gallon.

QUESTION #1: Is this guy telling me the truth about Lumens? I did not think Watts could be accurately converted to Lumens? You're comparing apples to oranges, right?

QUESTION #2: I am looking at an 8 tube high output fluorescent light fixture. The lights put out 432 watts all together at 6,500k, and cranks out 40,000 lumens. Would this be sufficient for my Amazon Biotope?

 

[SuperColey1]

I am working on a Biotope tank setup for a flooded Amazon stream and the plants for such a biotope all require bright light (Cabomba, Amazon Swords, Helzine, Milfoil, etc...). The tank will be 75 US gallons (285 liters) and the height is 20 inches. I will mostly have Angelfish in the tank.

The gent at my LFS was telling me that for this setup I would need 3-4 watts/gallon. But... he then says to me that this is not really the case because it's the "Lumens" of the light source that really matter the most. Seems logical to me because watts is just a measurement of power being used, and not of actual light intensity. He also tells me that 1 Watt = 680 Lumens (at human eye sensitivity of 555 nanometers). So... this somewhat translates to 2,000-2,700 lumens per gallon.

QUESTION #1: Is this guy telling me the truth about Lumens? I did not think Watts could be accurately converted to Lumens? You're comparing apples to oranges, right?

QUESTION #2: I am looking at an 8 tube high output fluorescent light fixture. The lights put out 432 watts all together at 6,500k, and cranks out 40,000 lumens. Would this be sufficient for my Amazon Biotope?

I think this is a LFS guy geting his facts a little mixed up.

I may be wrong but as far as I know watts has noe relativity to lumens. I think you are right in that 2 different type of same wattage bulbs can have different Lumens.

He is also wrong in the 3-4WPG statement. This is quite an old way of thinking.
3-4WPG is used by many for fast growth. for example building atank for a show or photoshoot where you want everything to be fully grown in a few weeks/months. For a long term tank you should be able to grow virtually any plant with 2WPG.

With a tank as largte as a 75USG the WPG rule also means that you need less than for a 20-40USG tank so 2WPG would move up towards the high light regions anyway. (In general Nanos need a lot more than the WPG rule and large tanks less)

There are some that say the light spectrum is the most important thing to consider i.e. pink lights are better for plants and daylight 10000K produce more algae.

There are some just as (or maybe more) knoweldgable that currently state that the light spectrum doesnt matter one iota and that watts is what matters.

I sit somehwhere in between these 2 statements as I have pink and daylight and am happy with the results.

Also consider what size of tube you are using. HO T5/T5 HO will be much more efficient and will have much less 'restrike' from the reflector than a T8. I assume you do have reflectors as these are partof the WPG rule.

Again there is some debate over how much more light comes from T5HO compared to T12 (which the WPG rule was calculated with) so its a users job to make their own jusgements on this. I calculate at 2x giving me 1.8WPG x 2 = 3.6. Others say 1.25 x. There is no strict ruling on this and I would say it is your judgement on how your plants do that will determine your own answer to this equation. This works its way down the scale of lights meanin that T12 =1, and T10, T8, T6, PC and T5 are all ascending multiplications of light.

As for your plants. Cabomba, Echinodorus will gorw in as low as 1WPG The large plant in my sig is an amazon sword which I ripped out due to it getting too large under 1.1WPG!!! Cabomba will grow as long as there is a torchlight there <---dont try this it is a silly exaggeration. The picture incidently is taken with .6WPG of a daylight on.

My 125Ltr tank is 20" and the rule is supposed to work for anything below 2ft so you dont need to take into consideration the height in your case.

I guess what I am saying at the end of the day is if you have 110W then you are on 1.5WPG. If they are PC then you can multiply it. If you dont have reflectors then get some. If they are 3" from the water there is no problem, mine are about the same. So the only thing you need to do is get some reflectors if you dont have some and better tubes if you dont have them already. What tubes do you have.

Andy

 

[Piscator]

I guess what I am saying at the end of the day is if you have 110W then you are on 1.5WPG. If they are PC then you can multiply it. If you dont have reflectors then get some. If they are 3" from the water there is no problem, mine are about the same. So the only thing you need to do is get some reflectors if you dont have some and better tubes if you dont have them already. What tubes do you have.

Hello Andy,

Thanks for the prompt reply! It looks as if the light fixture I bought is overkill for my application. The unit has two switches - each of which turns on four of the tubes, so I can moderate how much light is being made.

The fixture does have a mirror-like reflector, and the bulbs are T5-HO "Spectralux" 54 watt bulbs at 6,500 kelvin.

 

[SuperColey1]

If all the bulbs are 6500K then I assuming you have a very pink looking tank. lol

If you can switch 2 and 2 then just use 2 for your main photperiod (9-12 hours) and the other 2 for a noon burst (2-4 hours in the middle)

I would also replace 2 of the pink lights with daylights to balance out the colour from pink back to a more'natural' look to the human eye. I am of course meaning 1 of the main and 1 of the noon.

I would also make sure you absolutely pack the tank with plants (75% coverage) to combat algae because as I said below T5 HO is going to give you 'more light' than the WPG works out at.

As for what the guy said. 1W = 680 Lumens if you buy a tube that is 1W=680 Lumens. lol

Andy

 

[Piscator]

If all the bulbs are 6500K then I assuming you have a very pink looking tank. lol

I do not have the tank set up yet - not even a drop of water in it. LOL! But, I thought that 6,500k was in the cooler blue range? Every Kelvin chart I look up shows it this way.

If you can switch 2 and 2 then just use 2 for your main photperiod (9-12 hours) and the other 2 for a noon burst (2-4 hours in the middle)

I can only switch on 4 and have the other 4 off - not 2 on and 2 off. Am I understanding you correctly? Maybe not, eh... Or, do you mean remove 2 from each set of 4 lights, and just use 2 from each set? (leaving 4 sockets empty)

I would also replace 2 of the pink lights with daylights to balance out the colour from pink back to a more 'natural' look to the human eye. I am of course meaning 1 of the main and 1 of the noon.

I can go back to the store and switch 4 of the 6,500k lights for 4 of their 3,000k lights. This would create a more "natural" light cast, correct? But then, would this not also cast light frequencies that algae are fond of?

 

[SuperColey1]

I thought that 6,500k was in the cooler blue range? Every Kelvin chart I look up shows it this way.

Daylight tubes are usually in the 6500-10000 range. Mine is 7500K. Most Pink lights for plant growth are usually in the 4000-6500 range. Mine is 4500K.

3000K would be like a shop fitting or house flourescent which are normally 2700K. It may also be like the 'beauty' lights which give a more yellowy glow. Generally with the K ratings the lower is warmer light and the higher is colder. Marines are normally 9000 to as much as 20000!!

I can only switch on 4 and have the other 4 off - not 2 on and 2 off. Am I understanding you correctly? Maybe not, eh... Or, do you mean remove 2 from each set of 4 lights, and just use 2 from each set? (leaving 4 sockets empty)

That was me not reading. lol

I can go back to the store and switch 4 of the 6,500k lights for 4 of their 3,000k lights. This would create a more "natural" light cast, correct? But then, would this not also cast light frequencies that algae are fond of?

I would go the other way. The 6500s will be at the top of the pink range. 3000 will be yellow and your tank will look very strange. If you get something in the 7000-9000 range it should balance the pink by adding green and thus making it more natural to your eyes.

Andy

 

[phishstixx]

CFL vs Incandescent - Watts and Lumens
Power of the light, Colour Temperature and Shape are some of the considerations when deciding which CFLs (Compact fluorecent lights) are the correct replacements. Below are some details on Lumens (Power of the light), Colour Temperature and Shape;

Lumens (power of the light)

Match Lumens to the incandescent lights you are replacing. Lumens indicate the amount of light being generated which is different to watts which measure the amount of energy used. the table below compares watts (for both CFL and incandescent) and lumens.

CFL Watt Incandescent Watts Lumen Range
8 to 10 40 450
13 to 18 60 890
18 to 22 75 1210
23 to 28 100 1750
34 to 42 150 2780


Colour Temperature

Choose the color temperature that’s right for you (Color temperature can be indicated in kelvins or mireds)

Color temperature kelvin mired Notes
Warm white or
Soft white ≤ 3000 K ≥ 333 M Similar to incandescent
White 3500 K 286 M
Cool white 4000 K 250 M white/blue
Daylight ≥ 5000 ≤ 200 M


CFL Shape

Compact fluorecent lights are available in a large range of shapes that can fit the majority of existing lamps and lighting fixtures. Some of the shapes are Candelabra, Flood Lamps, Globe Lamps, Spiral Lamps and Standard Lamps.

this is something i found online somewhere. Here is also a link more related to light with-in aquariums
http/woo.gotdns.com/Aquarium/Lighting.htm

 

[SuperColey1]

Color temperature kelvin mired Notes
Warm white or
Soft white ≤ 3000 K ≥ 333 M Similar to incandescent
White 3500 K 286 M
Cool white 4000 K 250 M white/blue
Daylight ≥ 5000 ≤ 200 M

This is wrong!!

Pink lights are where you have but the cool white. cool white (white/blue is over 10K as per marine which it is intended for!!

As for Power Compacts. Several of us in the UK have moved away from these as they tend to cetralise too much light in 1 area whereas T5 or T8 linear seem to spread the light better.

Andy