Has anyone noticed that there is no "Important Topics"
thread under reef lighting. Maybe this discussion should be under that heading. PAR, Lumens, Watts, WHAT??
Watts per Gallon is the easiest way for someone to describe the way to light a tank because... It's a label on the bulb. Be it Metal Halide or a Fluorescent. You could talk PAR or Lumens or Spectral energy or Newton Meters to someone all day long and all you would get is a blank look. If you mention WATTS, then a light bulb turns on and their face brightens up because you're talking something that they have heard about and maybe even slightly understand.
So to make a long story even longer. What is important? The amount of useful light that reaches the Corals and animals that require it and it's intensity. Now how do you explain this to a Layperson and when are the lighting manufacturers going to start marking the bulbs with PAR values written on the side next to the wattage.
Definition - PAR photosynthetically active radiation is a measure of the amount of radiation capable of driving photosynthesis striking a unit area. It is given in the units of micro moles per meter squared per second (umol/m2/s).
In the applied plant sciences such as plant ecology and agronomy, there is a need for a simple system for measuring the light which is active in plant growth, analogous to the photometric system for measuring the light which is useful to humans in their daily life. The best likely candidate is "photosynthetically active radiation" (PAR).
Now ask yourself if you truly understand this definition and then ask yourself if the average person walking into a pet store for fish or live rock would understand it.
So debate all you want. Until they start handing out PAR meters like candy, or a PAR value at a rated distance on the side of the bulb packaging, you're gonna have to live with WPG.
Jim
