My opinion, tank size is unimportant. What matters is that water is moving all over and around the rock work meaning no dead spots. No one can say for certain that you have enough water movement by knowing tank size and or pump size, at best it's a guess.
The only way to tell for sure is to stir up some sand and or blast some detritus from the rocks and watch how stuff flows. Watch for dead spots and adjust the pumps or flow rate or pump program to accommodate, if you still have a dead spot them maybe time to add another pump or move to a different type of pump like a gyre of sorts.