[Simpte 27]

Am I wrong or is 20 watts 20 watts regardless of where it comes from? (Not taking into account the K ratings) But is 20 watts from a CF at 6500K the same as 20 watts from an incandescent 6500K or 20 watts from a flourescent bulb?

 

[niko]

One of the downsides of Compact florescent bulbs is the small distance between the 2 tubes. That results in light bouncing back to at least part of the tubes with some light loss as a result. I personally believe that that is very pronounced on this 96 watt Quad Compact fluorescent bulb.

The ballast that runs the bulbs also has a great impact. A good example is the IceCap 660 ballast - it underdrives the 110 Watt VHO bulbs resulting in what appears to me to be about 80 or so watts instead of 110.

The reflector that is another thing that has a big role. The popular AHsuppply reflectors really focus the light in an area right under the bulb.

Many dealers claim that their reflectors considerably increase the amount of light because of the special coating and shape of the reflectors.

I'd say that one doesn't need to chase exact numbers. Once again - it is the plant's appearance that will show if you need to adjust something.

If your question is about how much light to purchase I'd suggest that you start by providing your tank with 2-3 watts per gallon with the best bulbs you can afford and adjust the light later if needed.

--Nikolay

 

[gpodio]

20 Watts is 20 Watts no matter what is consuming it, but that only tells you the amount of consumed electricity, not the amount of light emitted. If you are thinking light emitted, then no, consumed wattage does not give an accurate indication between different types of lamps. If we are talking strictly flouorescent then T12, T8, T5 and CF bulbs are somewhat similar and can be compared by wattage to a certain extent. T12 are usually the least efficient and therefore less light per watt, followed by T8 and then by T5 and CF bulbs which are the most efficient to date. MH lighting is also similar to CF and T5 fluorescents as far as lumen per watt output. Incandescent on the other hand is far below the efficiency of any fluorescent lamp, you would have to look at lumen output to compare them correctly.

As Niko pointed out there are also issues regarding reflectors and restrike, certain shapes of bulbs are easier to direct where you need to using reflectors, MH and incandescent bulbs are probably the best shape, followed by single linear tubes (T12, T8, T5) and finally by folded or spiralled tubes such as CFs.

Hope that helps
Giancarlo Podio

 

[Simpte 27]

So when talking about aquarium lighting for plant growth, would it be more accurate to measure lumens over watts?

 

[gpodio]

It would be more accurate however also more complicated as not all bulbs give you a lumen rating. Not only that, but the amount of lumens also varies between different bulbs of the same type and the same bulbs when run by different ballasts. So as you can imagine it gets quite complicated. In the end, "Fluorescent and MH Watts" is the easiest method to use even though it is not as accurate as lumens. MH and T5/PC bulbs have similar lumen per watt ratios so they can be used in the WPG rule too. That's why when people say 3WPG, they usually also state that it is CF, T8, MH or other type of lamp which gives you a better picture than the WPG number alone.

Hope that helps
Giancarlo Podio

 

[Corigan]

So when talking about aquarium lighting for plant growth, would it be more accurate to measure lumens over watts?

One of the guy's at one of my LFS always has told me, "Don't go by the WPG rule, you know what really matters is the lumens.." I agree with him that lumens is more important than watts. As pointed out by Giancarlo though, it is much easier to explain to someone WPG than have them looking around for lumens on each bulb packaging. I think lumens would extremely complicate the process of helping someone out when the are first getting into the hobby. One of the guys at my LFS was showing me that these T8 Hagen glo bulbs had really high lumens that could be close to that of what is is being outputted by some of the CF bulbs. I still use WPG though since it's easier..

Matt