Panel 1: Elly scoops Frank out of his bowl and tells Mike that he's gone. Mike is horrified and asks "He died? How come? What happened?"
Panel 2: As Lizzie looks on, Elly puts Frank's remains on a piece of papaer towel and says that she thinks that he might have been overfed and his bowl could have been cleaned more often before saying that they (by which she means "he") probably didn't take too good care of him. Notice that she doesn't simply say that they don't live too long.
Panel 3: As he looks down on the goldfish he just got told he killed, Mike cries out in angusih as John looks on in confusion.
Panel 4: He then tells Elly that he's amazed 'cause Frank hasn't had THAT much attention since she brought him home.
Summary: Like I said yesterday, this is a bit of foreshadowing of Farley's death; he too only managed to become central to the story after he died. Before that, you could be forgiven for thinking that they didn't have a dog.