If you must have a pet fish, try this.
Your problem lies in the fact that you are dealing with a food chain, billion year-old instincts, and the fact that fish aren't trainable. The good news is that the solution can be found right there in the same realm. Try this:
1. Get a really big tank. 55 gallons is the smallest option. Landscape it with wood things and plants and nooks and crannies where little fish can hide.
2. Populate it densely with pretty fish of varying shapes, sizes, colors, and (this is essential) speed. Lots and lots of them and let them be the kind everyone likes to look at and enjoy. But be careful; you must have at least a few of each type swimming around in there. Your kids will undoubtedly try and name each and every one of them, and pick favorites. The happy truth is though, they won't be able to truly differentiate between individual fish if you have doubles, triples, and fourples of each. This is critical because these are your kid's pets.
For you the adult, however, resist any temptation to dub one of these fish your "pet". The Food Chain Factor still looms large, and you've already experienced the wrench of it's harsh reality when you drop the puck in that arena. Don't set yourself up for disappointment again, so....
3. Go buy 1 of something along the lines of a Gar (my favorite), Oscar, or Jack Dempsy. If you must get close to a fish, get close to one of these bloodthirsty SOBs. This particular fish (and only this fish) now becomes now YOUR pet. It's the one you care and worry about, the only one you have concern for when you are gone. The others?...your kids so-called "pets"? Well, to you they are just ordinary fish because none of them are as cool as yours! Hint: If you don't want to someday see them on Oprah, resist the temptation to tell them you feel this way.
4. Toss your pet into the tank with the ordinary fish, and....
Voila! Problem solved! Now you have no worries, because your "pet" is sitting pretty at the top of the food chain! Thanks to you, he's the HMFIC of your living room Waterworld, and there is food aplenty for him swimming around him that will stave off any unforseen aquatic famine. "Lunch" is right at his fintips thanks to your careful foresight and planning, and guards against a forgetful wife who will probably hate your cool, bad-a$$ fish in the first place because you love your pet so much and she thinks its "icky".
5. With all those ordinary fish swirling around in there, face it, nobody will ever be sure just how many there are, or if a few go missing. If upon arriving home you are queried by your kids regarding ordinary fish MIAs, find out exactly what kind they are talking about, then peer and squint into dark corners of the tank and say things like "Oh he's back in that driftwood, asleep.", or "he's down inside the castle, can't you see him?". As a last resort, secretly tap the side of the tank and keep tapping until there is a flurry of fish going round and round, and announce "Oh yeah! there he goes, there he goes! See? See? There he goes again! Hey kids who wants ice cream!"
6. Take the information you skillfully extracted from the kids regarding which type of ordinary fish were MIA....the aforementioned "sleeping" and "hiding"ones.. go down to the pet store, and buy some replacements. Return and secretly dump them in late at night and after your pet has been fed.
7. Don't get lazy and forget Step 6 or the tank's fish density will get too low and eventually you will get busted. Kids are smart you know.
