Double the drain pipe and put a gate valve on it after they meet. you can run a herbie like this get much more flow and very silent.
FYI my 120 runs one 3/4 the return, other 1" is tied into the opposite 3/4" into a 1.5" gate, the last 1" is the emergency line. I have a panworld 200.
Next tank I get will not be a reef ready!