no wont be hectic like a toilet flushing but you going to be adding extra bubbles to your sump from sucking air in the breather as the water passes so hope you have a baffel if you going dsb
Got a solution to that that I use.
Get a tupperware(plastic biscuit bow) and cut a hole in the lid the same size as your return pipe. Also add a 1" breather hole to the lid.
Fit it lid first just above the waterline and drill a holestraight through the return pipe to allow a plastic dowel to slide completely through holding your lid in place and to stop it dropping off.
Next take the box itself and drill heaps of 1" holes in the bottom.
Fill the box with filterfloss and install the box which will now have its rim just above the waterline
Bingo no more micro bubbles