He's emailed me saying fish 'grow to as big as you feed them to' what? Am I stupid or is he? is he saying you stop feeding a fish when they're the preferred size? he also said fish don't outgrow tanks. Am I missing something? This is the weirdest thing I've ever heard.
What you do is, when your fish is a couple months away from its ideal size, you stop feeding it. By the time it reaches the size you want, it will be weak and sickly and won't grow as much, so then you can throw it away and buy a new one. At that point, technically, the 30 gallon aquarium has lasted for the fish's lifetime, nothing ever outgrows it, and the fish store makes more sales. It's a win/win/win, as far as I can see.
[Disclaimer: I'm joking]