heating for cresteds

[Ducksarefun]

I've been avoiding posting what will probably seem like a stupid question, but I can't seem to find the answer I am looking for.

We will be getting some cresteds soon, two actually, and until they grow up a bit they will be kept in a 10g. It was originally a fish tank, so I have the flourescent light fixture that came with it. Right now the temperature is between 65-70 degrees in there with no light on and the aquarium lid.

When we actually have geckos in there, with a screen lid of course, will the strip light (15 watt I think) be enough heat?

What does everyone use to heat your crested tanks?

Thanks!