Nems are beautiful creatures and the symbiotic relationship with clownfish is something very special. I love nems. Have several. Killed several because I was impatient. I gave up trying to keep them after several were killed. I didn’t try again until my tank was about a year old and they thrive. People would always say the tank was immature, but I didn’t want to believe it. Believe it. It can’t be clearly explained because honestly, I don’t think anyone knows. One thing for sure, tank maturity is definitely an anecdotal thing that I agree with. Now, since you got it as a gift,not much you can do about that. Maybe a LFS will take it for credit? I know it sounds harsh, and I don’t mean to be, but my experience is that it will not thrive. It might, and I would be happy if it does, but it probably won’t. Someone in a thread here explained “tank maturity” like this and I thought it was great (paraphrasing): “are you more comfortable in a clean sanitary room or your grandmas house with all her stuff filling every room?” Now, if you have a hoarding grandma that would be a different story, but I get the picture. Good luck.
The clown in the pic is about 2”