I guess in answer to your question's...which were confusing

1st In bio bucket system generally the rez in topped off and never totally changed.

2nd. As far as feeding thru top...If you are concerned about rez agitation, you could run feeder tube all the way to bottom of bucket, but none of this stuff really matters, because you have already built your system.

3rd...extra valves to redirect flow, already have them.

well goodluck, there isn't much I can do for you. I put your thread in my sticky, so it will be there for people to come across. lw