MDH what was your point in posting that thread??? ya no kiding I know fish in wild can't grow to the same size as a tank. That doesn't mean we should all skip the big tanks and buy a dovii to put in a 10 gallon. We can't grow a fish to its wild size although we can do our bests to get as close as possible. We shouldn't be putting a fish that should grow 16" in the wild in a 30 gallon tank so it can only grow 6". Ever hear the saying "fish grow to the size of the tank"?? Well the truth is fish die to the size of their tank.
I don't understand your logic, if there really is any???
To be a responsible owner you need to make an attempt at making the best size tank possible.
piggy your fish will be fine. It may be stressed for a little while in that tank but as long as your keeping up with water quality your fish will be fine once you move him/her into the 90 gallon.