Those bulbs do give little light but they do produce some heat. I bought aquarium LEDS off ebay so they wouldnt actualy be part of the heating in my tank (so I could turn them on and off when ever I please and not affect the temp)

http://cgi.ebay.ca/ws/eBayISAPI.dll?...TODAY.m238.lVI

After I bought this, I was a little cheesed to find those tiny betta night lights that actually plug in. I thought they all ran on batteries (grrr)