BLB, Black Light Blue, is a tube using a woods glass filter they are one's that look black / dark purple this allows the light to filter out most of the visiable light from the tube. And the BL is just a Black Light they are white but light up blue, normally seen in bug zappers...
I think most guys here know the difference..and just suggested BL as an alternative to BLB since they're sometimes easier to find.
The Actinic-03 I mentioned is white when off like a BL, but when lit its a much deeper blue than BL (still not that of a BLB though)