how hard would it be for the guys who have multiple tanks to take like a 55 gallon tank an make it into a like a overflow an just have one big filter to run all tanks?
not any more tricky than doing it for a single tank, if you can handle that, you can handle multiple.
nof if you want to do it all from a single pump then you'll have to do the amth to calculate flowrate but beyond that equlizing the flow is as simple as makign sure the overflow can handle more flow than than the inlet. That's the nice thing about an overflow, as long as it's big enough it will never be too much as it will always match the pump flow rate.