what matters more

[remme]

two tanks...same filtration but one is 30g the other is 75g...which is more important for fish growth..space or water quality....
will a fish grow faster in a smaller tank with amazing waterquality or in a larger tank with below par water quality?

 

[JSchmidt]

Both are important. Deprive a fish of sufficient space for it to behave normally and it will not be healthy. Deprive a fish of clean water and it will not be healthy. Depending on the species involved, either could be detrimental to a particular fish.

Is there a particular type of fish you'e wanting to keep? We could probably help you decide what size tank would be required to house it adequately.

Jim