A bunch of years ago, my middle one was about 3 or 4 and had a friend over. There were 4 adults in the next room. After one was spotted standing on her tippy-toes pouring something into one of the tanks, you just wouldn't believe how much and how many different things they poured into a 29G to "feed the fishies". Every flake, medication, water treatment got dumped in there. In a matter of 30 minutes you couldn't see to the back side of a 29G. And no, not all of those things would've been good for a 4-year old's health. Kids are a trip...........a journey..............an odyssey.
Ya gotta watch them for sure. For the fish' sake too.
"Why can't my wife see all of this stuff as an investment?"