Growth Rate and tank size

As the tank gets larger, the need for more and more space isnt so important....

For example: I usually recommend 20 to even 30 gallons per Goldfish for people who have these fish. This doesnt mean that for 5 Goldfish I expect them to go out and buy a 150 gallon tank! The 20 to 30 gallons is a measure to start off with. After the initial fish is added into the figure, things get easier and you can start to go more towards the 15-10 gallons per fish figure.

This is a goldfish example...it doesnt work for all fish but you get the idea of what I was saying hopefully.