[jeffhardy55555]

in my 30 gallon tank i have 2 incadesent fixtures so i decided to use the screw in flouresent bubls, they only consume around 25 watts of electricity but they output 100 watts of light each, is this sufficent to grow plants?

 

[Erirku]

HUH?
So, you say they use only 25w an hour or whatever the deal is, and the output of lighting is 100W X 2= 200WPG that means you have 6.67WPG, way too much light, and alot of new unwanted growth (algae).
Incadescents aren't that great either, they have a tendency to make the water warm or hot and aren't that great for plants for photosynthesis. If I were you I would get rid of that and go buy a compact fluorescent fixture for aquascaping. If you can't afford one, then I would go with www.ahsupply.com for money savings. Hopes this helps?

 

[Mnemia]

HUH?
So, you say they use only 25w an hour or whatever the deal is, and the output of lighting is 100W X 2= 200WPG that means you have 6.67WPG, way too much light, and alot of new unwanted growth (algae).
Incadescents aren't that great either, they have a tendency to make the water warm or hot and aren't that great for plants for photosynthesis. If I were you I would get rid of that and go buy a compact fluorescent fixture for aquascaping. If you can't afford one, then I would go with www.ahsupply.com for money savings. Hopes this helps?

He's referring to the screw-in compact flourescent lights that are made for lamps, etc. From what I understand these are not very suitable at all for a planted tank...light largely isn't directed downwards into the water, since they're meant for projecting light in all directions. They're also sort of small so I can't imagine that they would do a good job of evenly distributing light in the tank. They aren't incandescent, but they're not good for an aquarium either.
I don't think the watt/gallon rule could actually be applied to these bulbs since they're entirely different from normal aquarium lighting and "watts" aren't really a measure of light output but of energy usage. The "100 watts of output" thing is definitely completely irrelevant because that's just a comparison to the light output of a 100-watt incandescent bulb. All the "watts" in the wpg rule refer to fluorescent watts.

Your advice still stands though. He should get a good PC fixture and use that. They're relatively cheap for a 30 gallon.