Light reccomendation

A ten gallon tank, with a standard 2 bulb, screw-in light hood can be adequate for low light, non-CO2, with screw-in CFL bulbs, 14 or 15 watt bulbs, if you have some kind of reflector, or a white painted inside of the hood.

For a 40 breeder, three T8 bulbs, 3 T8 single bulb strip lights, will give low light. Or, a PC, single bulb 3 foot fixture, with a typical poor reflector, will give low to low medium light. Or a one bulb T5NO, 3 foot strip light, if you can find one, with a DIY reflector should give low medium light. If you can suspend the light above the tank, a single T5HO, 3 foot fixture, suspended about 6 inches above the top of the tank, should give you low medium light.

Hoppy I seen your chart, but how do wattage factor in?

ahud said:

Hoppy I seen your chart, but how do wattage factor in?

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Wattage does not really factor into the amount of light that you can have/put over an aquarium.

With newer technology, light bulbs have become more efficient, and as such, consume less power for the same amount of light being emitted.

As such, wattage does not really play a role at all in the grand scheme of things. This is why the WPG guideline does not really apply anymore, especially with the advent of T5 and T5HO bulbs. It does not even really work that well for T8 bulbs anymore. For example, 2 WPG of T12 lighting would be very different from 2 WPG of T5HO lighting.

The only place where wattage figures in is with the screw-in spiral CFL power saver bulbs, all of which are about the same size, but, because the tube that is wound into the spiral is of different lengths, they can be made with different wattages. With those, the higher the wattage, the more light you get. You can't use a watts per gallon number with them, because it makes a huge difference whether the bulb is vertical above the tank, or horizontal, and whether the light is in a good reflector or none or a poor one. And, of course, it is the height of the tank that is more important than the volume in gallons of the tank.