Here's some better bulbs that would fit into your light fixture
http://www.drsfostersmith.com/produc...&N=2004+113346 they are 10w but shines as bright as 50w for only $9.99 a bulb and right now one of the three different types are onsale for $4.99 this is what I was going to get for my 10g but am now switching it over to a 20g some of my plants looked fine for a while and then they started dying off because of lighting