[Auto-Post] Weekly Question Thread! Ask /r/aquariums anything you want to know about the hobby!

So, I think I've made a mistake on my aquarium. I just set up a 180 gallon tank with a Fluval FX6. The problem is I'm just now reading about the cycling process and wrapping my head around it. I've got a few goldfish in it, and was wondering why I had 3-4 die the first few days. I feel awful, but now just want to know what I should do. Everybody is eating and acting normal (they've been in there about a week), and there haven't been any deaths. Is there something I should add, or has the worst of it now passed and we are in good shape now. I now know I shouldn't have started it this way, but with a tank that's up and running I'm totally unsure on how to best continue from here.

/r/Aquariums Thread