I was going to add an 'all of them' option but everyone would have picked it I think... I want to know the MAIN thing that causes all the enjoyment (even though they all do!)
I love watching them. Like getting to know their personalities... Well, as much as there is of that. Most of all, I love watching my 4 year old child enjoying them. It seems he notices something new every day.
Man...tough question! The sheer entertainment factor does it for me...The Fish's individual personalities, the tank maintainance...the fact that guests to our home enjoy the tank more then our company...Hmmmm. Perhaps this says something about either fish keeping, or our hospitality...
Nothing is better than doing weekly water changes. You get the glass all clean and afterwards the fish seem to perk up and become a lot more active in the fresh water.