A 55 gallon tank is fine for any fish, no matter how big it gets. Here is why:
Take your average fishkeeper. They think of fish as decorations, not as pets. They perform water changes when there is obviously a problem. They are too lazy and cheap to buy a water test kit, they just bring the water into the store, along with the dead fish they just bought. They think that a fish will grow to the size of the tank, and they are right. It will be dead long before it's time to buy a new tank. They ask me for a fish that eats algae, because they are too lazy to scrape it, and they are too cheap to buy a magnet scraper, even though the supposed "Algae Eater" is just a few dollars less. They ask if there are fish or snails that eat "fish poop". (Where exactly does this fish poop go after they supposedly eat it?) They reject the notion that fish are incompatible. They ask to buy magic pills that they can drop in for a sick fish, even though the reason for the disease is probably at least partially related to water quality. They don't want to cycle, they want to "try it anyway". They buy fish with plans to give them away when they get to big. They reject an experts advice because what they want to do is more important than the fishes well being.
There are average fishkeepers, and then there are MonsterFishKeepers.
Sorry but I work in a fish store, and I see all to many of your "Average" fishkeepers.
Take your average fishkeeper. They think of fish as decorations, not as pets. They perform water changes when there is obviously a problem. They are too lazy and cheap to buy a water test kit, they just bring the water into the store, along with the dead fish they just bought. They think that a fish will grow to the size of the tank, and they are right. It will be dead long before it's time to buy a new tank. They ask me for a fish that eats algae, because they are too lazy to scrape it, and they are too cheap to buy a magnet scraper, even though the supposed "Algae Eater" is just a few dollars less. They ask if there are fish or snails that eat "fish poop". (Where exactly does this fish poop go after they supposedly eat it?) They reject the notion that fish are incompatible. They ask to buy magic pills that they can drop in for a sick fish, even though the reason for the disease is probably at least partially related to water quality. They don't want to cycle, they want to "try it anyway". They buy fish with plans to give them away when they get to big. They reject an experts advice because what they want to do is more important than the fishes well being.
There are average fishkeepers, and then there are MonsterFishKeepers.
Sorry but I work in a fish store, and I see all to many of your "Average" fishkeepers.
That's pretty funny! A full grown silver would probably freak out so bad from being crammed into a 55, that it would jump out in about 30 seconds! 
people are idiots!
