What the Mrs. doesn't understand yet is that fish keeping can be and is extremely educational. You have to learn biology, chemistry and environmental sciences in order to keep a tank well maintained ( and math if you mix too many male and female fish together ;D.) In fact, if the tank is kept properly, you shouldn't have to spend much time on it. My 6 tanks and 2 betta bowls don't take me more than an hour each week to maintain. My favorite saying is " The less you mess, the greater the success!" That means do it right the first time and you will have better success and less cost.
There is another positive to fish keeping at an earlier age. In my case, I started when I was 7 years old. That love of fish blossomed into a 40 year career in the fish business. That entailed travels abroad, (which expanded my understanding of other cultures) understanding genetics,( I became a fish breeder for most of my career), and becoming an environmentalist ( By understanding where the fish came from and visiting those areas, I was better able to recreate those habitats in my tanks as well as encourage others to be more environmentally friendly in their lives, which we all know is the key to our own survival as a specie) as well as a financial reward.
When I got married, my fish were just part of the package ( along with my Monkeys
) My wife didn't know a thing about them, didn't want anything to do with the care and upkeep of them, but sure liked the results I got from them. And of course, when I gave her books to pick out fish she would like me to have in the house, her tastes were well over our financial means ( and the pictures didn't come with price tags, she just liked the rare and distant stuff. lol) Although we are now divorced, in a recent conversation with her, she admitted that she missed having a tank in the house. Fish do rub off on people
Hope this helps