yes, the one-inch rule doesnt apply to goldfish..
it only really works for small fish that get to one inch, then stay one inch!
like tetras..
the problem with goldfish is mass..
a one-inch long goldfish is a much BIGGER fish than a one-inch long tetra!
fatter, wider..
and think of "10 inches of fish"..
by using the "one inch per gallon" rule, you can fit 10 one-inch tetras in a 10 gallon tank right? yes, you can..because they are 10 *small* fish..
but now think about a 10-inch long goldfish!!
its still "10 inches of fish"..but the one goldfish has many many times the mass of the 10 small tetras, and can barely turn around in a 10 gallon tank!
also, because goldfish are cold water fish, their water holds less oxygen than warmer, tropical water..
and they are generally "messy" fish, the way they eat results in dirty water, which means you need more water volume per fish, and more water changes..
and you also want to have a tank that accounts for the future size of the fish..
yes, 4 1-inch long goldfish might look lost in a 55-gallon tank!
it might *seem* like overkill, but the fish will grow fast, especially if they have good conditions..
lets say you want to own 4 goldfish and keep then for a decade!
would you rather just start out with the 55 gallon right away, and never have to buy another tank or move the fish..
or start with a 10 gallon, then buy a 20 gallon when hey get too big for to 10 gal, then buy a 29 gallon, then a 40 gallon, then a 55 gallon, etc..
it would be much easier, cheaper (in the long run) and much better for the fish to just start out with the proper, big tank int he first place..even if you buying 4 teeny baby goldfish..
same thing with only one goldfish..much better to start out with the 20 or 29 gallon tank right off the bat..that one fish will have a nice roomy home to grow into..
I just made this!
Scot