adding considerable volume to system input?

I plan to add a55 gallon drum to my 40 reef over the next week. With fresh mixed water and adding bar rock over the next few months. I have added volume before at a trickle in. But never at a volume higher than the tank itself. The drum will be the end line and serve as the return to the tank and filled with base rock to be live rock in the long run for high biological filtration with the current sump shifting over to a dedicated refugium role and shrimp hatchery. If the water is well set and heated up my question is if the water is trickled into the system over three days to a week's time.. I shouldnt see any issues in the tank right?

I mean I know there will be no cycling or real wild swings esp if I start the trickle after a water change so they are close to thesame baseline. I just feel like I am missing something. Its mainly the volume addition That is geeking me out.


thoughts...?