I would be thankful for any comments on opening lines for this specific variation as I was not familiar with it. I was able to play by the seat of my pants as I am familiar with other fianchetto variations of the Gruenfeld...

Not sure what the Gruenfeld opening has to do with losing to a middle-game tactic.

Looks like you just didn't see 18. Nxd5 coming.

 I did not post the game to discuss the knight sac, I want to know what other Gruenfeld players are using and why they chose it. I have spent enough time looking at my middle game error on my own and it is clear to me where I went wrong (both psychologically and from a technical perspective).

I don't like the ...c6 Schlechter lines, but that is just a personal preference.  I look for an opportunity to take on c4 if my opponent doesn't first take on d5.  What your opponent did is he took you into a Slav exchange structure and when you played ...e6 your light bishop was locked in.  Perhaps you could have challenged his queen with 8...Nbd7 and then ...Qb6.

Thanks, ghost. I will certainly consider these suggestions the next time this line comes up.

Yeah, I play 3...d5 or 4...d5 vs the Fianchetto, the ...c6 lines always seem too passive.