Which uva/uvb/heat bulb is best ?

Question

for a 30 gallon tank?? the EXO-TERRA SOLAR GLO 125 w? powersun 100w? or t-rex 100w?

Answer 1

Depends on what kind of reptile you are housing.

Answer 2

Shay nailed the main point.  How far away does the product need to be from the reptile, and in what kind of habitat?

Here's a study you might wanna peek out:

http://www.uvguide.co.uk/

Remember when you're looking at those pricier UVB sources that they have to be replaced every 6 mo.

Sorry I couldn't be of more help.