Fluorescent Input vs. Output

[Moonshadow54]

I have seen much of what appears to be mis-information on the net about fluorescent lights. I just purchased two Coralife 50/50 compact bulbs. They are 20 watt each but are equivilent to 100w incadescent. I have a 60 gallon tank and I already have a 250 watt MH plus two 32watt actinics. Now what I have seen it that when people figure watts per gallon they are looking at the what the bulb uses for power consumption rather that the output of the bulb. I have found that most all fluorescent bulbs have a lumen/watt output of about the same. Am I incorrect in assuming that I have 250 watt Mh, plus 200 watts 50/50's and the 2, 32 watt actinic bulbs from what I have found is the equivelent to 130 watts each output. So total wouldn't I have 710 watts total output of light, and I am consuming 354 watts of power?

 

[fsn77]

Watts per gallon was a guideline developed based upon normal output T12 fluorescent lighting. It truthfully does not carry over well to the more modern lighting systems used on reef aquariums (MH, T5 HO, VHO, PC, etc.). The output of 250w of MH does not equal 250w of normal output T12 fluorescent, for example, which is what I'm guessing you're implying. I've heard some "conversion factors" that are suppose to help normalize the more modern lighting types to the watts per gallon guideline, but the guideline itself is still just that, a guideline, and not a very useful one. It doesn't work well with smaller tanks, tanks that are taller than average for their volume, or tanks that have atypical dimensions.

The only definitive way to quantify output would be to measure it directly with a lux meter or a PAR meter. Either of those will provide a much more accurate picture of the actual lighting conditions in a tank and are more useful for comparison. For example, if coral X is known to grow well in someone else's tank at a spot in their tank that receives PAR = 250 and you wanted to know if there's a suitable place in your tank where PAR = 250, that is easily measurable with a PAR meter and PAR is PAR regardless of the lighting type.

 

[charlie4486]

^ that is correct. i have also been noticing people using the wattage used as the wattage output. i just try to let them know that just because it only takes 13w to power it is the light equivalent of a 40w.

 

[Sploke]

Correct...wattage is a measure of power usage. Lumens and PAR will help to understand how efficient a particular bulb is. Sometimes we don't know the exact PAR rating of a parricular bulb, so we assume that its got a halfway decent PAR rating and say ok, 2wpg of energy usage should provide enough light for these plants.

This is a good synopsis of how it all kind of fits together:

http://www.sunmastergrowlamps.com/SunmLightandPlants.html

 

[Moonshadow54]

Thanks,
All I know is my tank and fish look really good with the lighting I have. Any brighter I think I would have to dig out my RayBans to enjoy the tank. I have not added corals yet as my tank is only about 9 months old, but I think after the first of the year I should be ready for them. Thanks again for all the input. (and output)