Quick question about en passant.

I don't know how to link to specific moments in games, but please on my game link, and scroll down to moves 29.

http://en.lichess.org/analyse/a7f1hkez

After black pawn on A7 moves to A5, why was my white pawn on B6 not able to capture black pawn via en passant? I'm just looking to increase my general chess knowledge. Thanks.

that isnt en passant, en passant would be possible if your pawn was on b5, not b6

Thanks for your response! I guess thats because black pawn had the opportunity to take my white pawn, whereas in en passant, neither pawn is afforded the opportunity to capture. I think.