Pet fish are seen as 'low maintenance' and while this is true to a degree, they do have specific needs and care methods alot of people miss, and i actually wouldnt suggest them as a pet for small children at all

1. they require more then people realize: most fish should be fed a variety of foods, need alot of fish buddies to be happy (if theyre a social fish), and also need alot space, my dad got me a 3 gallon fish tank with 8 tiny fish and two immediately died, and now my tetras (which arent as peaceful as advertised) are attacking my other fish because they dont have enough space to establish territories and are stressed from having such a small school, since they usually school in groups of thousands in the wild. (whats crazy is the person at the pet store said the tank was big enough for the fish which isnt true at all, so remember when buying pets in general the ppl who work there are tryna make a sale, make sure to do your own research before talking to them)

2. filters dont do everything, and neither do catfish: clean your damn fishtank. your catfish may eat left over food and some eat algea, but your water still will fill up with nitrate that needs to be removed even with a filter. if you have live plants they will help with cleaning the tank, but you should still do 30-50% water change every 1-3 weeks depending on how efficient your mini ecosystem is at cleaning itself up
   (if you dont have plants AND you dont have fish that help clean the tank, just clean the tank every week bro dont be lazy, your fish are literally swimming in their own pee and poop )

3. DONT TAKE YOUR FISH OUT OF THE TANK: yall you dont need to pour all the water out to clean the tank, just scoop out a decent amount of water, and replace it with conditioned water. this dilutes the old dirty water and is less stressful for the fish, also, changing the water completely can make your fish die of shock bc their bodies were used to the old water. you dont need to remove your fish or decorations from the tank to clean it.

(im am not a professional and still learning how to care for my fish so dont clock me yall)
i actually have lot more to say but thats all for today, lemme know if yall are interested in hearing more abt my fish care journey or whatever:P