I've read several articles from several places about lighting and I just don't get it. I haven't thought much about lighting and I'm just now trying to learn about it. I wanted to find out if I have low light or what, and if it is right for my tank. I assume my tank is ok because it is part of a kit that I got from a reputable manufacturer. Maybe. Anyway, my tank is 37 gallons, 20 inches deep, and the florescent bulb says 17W.

But, when I try to use lighting calculators or the "standard" of 2 watts per gallon for my typical setup, it just doesn't make sense. The math makes it look like my 17W is terribly undersized. It looks bright to me. ?

I have basic community fish, no live plants, and no direct or indirect sunlight. I have the light on for 8 hours per day.

Can anyone explain this?

Zambize

Without plants 17 watts is probably enough if it looks bright enough for you. You might have horrible algae blooms with more lighting. If you were to put plants there is a cool calculator at http://www.fitchfamily.com/lighting.html. It uses a theorem based on Takasi Amano's planted tanks

Oh, and moonlight. The same articles mentioned using lunar lights to replicate moonlight. Anyone think this is necessary, or recommended?

Zambize

My brother has two 15 watt lights in a 30 gallon planted tank. The light seems bright but its not enough to grow high light plants like glosso. The anubias and wendtii and wisteria do great as well as a couple others

Out of curiosity, is there any reason why you would be interested in upping your light? If its for the Java Moss I can assure you that it's probably fine with what you have and will just grow slow. But if you were to calculate....you're just under 0.5wpg. Were you ever to consider getting what falls into the category of ''average'' plants, this would be incredibly inadequate.

Try to think of it in terms of radiation instead of the intensity of what you see. the 86w light I have over my 30gal looks about the same as the 15w I have over my 16gal. It's also easy to tell I only have 15w over the top of my plants in there cause they grow at 1/4 speed of the plants in my new 30gal. Plants are absorbing light you can't necessarily see. Some of the radiation is lost in the glass just below the light, some at the surface of the water. So the greater the wattage doesn't necessarily equal more blinding light.

Another thing to consider is the kelvin scale. Optimum plant growth is considered to occur between 5400-6700 kelvin. This is simply put...to what degree the light is white. You may have noticed some tanks with a very yellow hue, and some which are bright white. The higher the kelvin the ''whiter'' the light. Marine tanks use 10,000k and up. I guess the UV from the sun and the way it refracts in the ocean has something to do with how demanding corals are for a much higher kelvin than plant growth.

6700k is a nice white light and what's considered closest to actual 'daylight'.

The 30 gallon looks great and is bright on the top but not all the light penetrates the plants. The fish have plenty cover. In my profile picture the two lights have different bulbs the left bulb is a Color intensifer from lightning rod and the right is a dual day actinic 10000k from lightnig rod you can definitely notice the difference in spectrums. The lightnig rod bulbs are cool because instead of being t8 bulbs they are t6 bulbs that produce 30 to 70 percent more than a typical t8.