Is 40W of light is enough for a fish only 30G tank?

[sasha]

Hi guys,

I am in the begining of adding watter into my 30G(45cm high) tank and one question pops up. The tank comes with Hagen canopy 2x20W halogen bulbs(Hagen Marine Glo+Power Glo), but according to the tank's manual, for marine aquarium I would need at lest 2W/Gal = 60W. Do I really need to add extra 1 or 2 of 20W bulbs (I guess Hagen Glomat2 could be handy) or 40W would be Ok for a fish only tank?