I just dont understand watts per gallon

tbone said:

All flouresent lights are pretty much the same wattage but theres a huge difference in the amount of light from light to light.

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Fluorescents come in a wide range of wattages. The amount of light is pretty similar from one wattage to the next.

tbone said:

For instance for clarity sake I'll talk about the "aqua glo, sun glo, power glo etc etc etc"…

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I don't know what any of those are. Don't pay any attention to the branding. The tech stuff isn't that complicated and will tell you wha tyou need to know.

tbone said:

then theres incandesantsthe ones they sell on those small tank kits wattages for incandesant lights is much much more then a flouresant. You cnat tell me a incandesant is better than a flouresant. Can you? The watts per gallon would say that it is though.

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The watts per gallon guidelines are specifically for Normal Output (NO) Fluorescents and have absolutely nothing to do with the much less efficient incandescents. There isn't any point in comparing apples to oranges.

Normal Output (NO) bulbs have a similar output of light per watt. They can also have various color temperatures and spectral profiles that can influence how bright they appear to be to some extent, but in general they're all similar. Length corresponds to wattage.

Compact fluorescents (CFs, also called Power Compacts or PCs) are slightly more efficient but are still fluorescents and are still similar to NOs. The big difference between NOs and CFs is size: Normal Outputs are much bigger than a Compact bulb of the same wattage (and similar light output).

The bulbs give off a particular color of light. This usually expressed as a color temperature in degrees Kelvin. The higher the number the cooler the light. Most planted folks try to stay between 5000k and 10000k. Salty folk generally go cooler, towards 20000k.

Each bulb also has a spectral profile. A bulb may have a lot of light in the blue and red sections of the spectrum and not so much in the green. It'll look kind of strange and not give such a great looking light. The manufacturer may smack a GroLight label onto the side of it. You want a more evenly colored bulb that actually looks good: if the plants get enough light they will grow.

WPG is a very loose guideline for specific types of lighting. It doesn't cover all situations, or all tank sizes and shapes. It's just used to give a rough idea of how much light you'll want for plants, broken into low, medium, and high light needs. I wouldn't worry about it--list what plants you want, if you want high growth/high ferts/CO2 supplementation, and what fish. We can offer specific guidance then, rather than just the general.