Why a six year old should not have his own pet

This is the third attempt to let my son have a couple of fish in his SpongeBob aquarium. First off let me say that we are nor fish-keeping novices. I have a large African cichlid tank in my front room with a specialty of those from Lake Tangyanika. We have a pond with several Koi. I have had been the guardian of an 125 gallon saltwater tank at a school where I taught and a South American community tank. I have learned many things from each tank I have kept:
1. Middle school students will pour Coke into a salt-water tank regardless (or perhaps especially because) of the fact that even a small salt-water fish costs fifty bucks. This caused interesting and catastrophic chemical reactions.
2. Plecostomus can crawl out of tanks and across the floor until they turn crispy. Pregnant self saw it, thought it was dead because it was dry to the touch, picked it up, and when it wriggled, screamed like a banshee and flung it onto a concrete floor because it spiked me. I finally got a shovel, scooped it up, and put it back in the tank where it slithered to the bottom and sulked at me for TWO WEEKS, which is pretty good sulking for something that looks like a prehistoric nightmare with a brain the size of a macadamia nut.
3. Do not put Advantage flea killing treatment on an elderly dog if there is the slightest chance that it can fall into your pond. Because, if you do, you will find that Advantage works by frying the nervous system of pests, and that fish that come in contact with even a few drops of Advantage in their pond water will basically have every neuron explode in their nervous systems.
4. Two year old Koi are too big to flush. They must be buried, if one wishes to avoid a painful call to the plumber. That means, if you have children, that you get out the Book of Common Prayer and read the Service for the Dead. In a serious voice.

But I digress. Back to my little fella and his aquarium....

The first time, Gary the Apple Snail turned out to be a bloodthirsty psychopath who wrapped himself around the Betta and turned him into disgusting goo-- and then he promptly died too. Explaining about the reality of the "Circle of Life" in explicit detail without a cute meerkat channneling Elton John is impossible, people. I mean, really, it's not like I bought him one of these:

The second time, someone had plugged in the heater and the air pump to the lightswitch. After not having the lights on for an entire December day, the poor little guppies were guppi-cicles. Oops.

This time, his sister came to tell me that he was carrying around one of the angelfish, and when I went to make sure the fish was back in the drink and still alive, I saw that someone had taken the fish food and turned the tank into something that looked like this:

Now, listen, I do not believe that any little beings should suffer unnecessarily. So I just spent fifteen minutes seining out the excess food with a net while the three little fish pressed themselves up against the glass and looked at me like this:

So this is it. I have confiscated the food, made sure the heater and pump is permanently on, and bought NO psycho snails.

But little pal, you are SO not getting a "hamstah."