Next to Merrill I fell in love with Aveline, but somehow I'm not able to draw her properly. So there was some frustration about that. I am sorry, Aveline. ;_; The friendship between her and Isabela was also one of my favourite things in the game.
I did the fish tank picture somewhat during ME2, when the effects of everything started to show on Shepard and I just wanted him to have a calm moment. Fish tanks seem to be perfect for that.