How small can return section be ?

I have a 20G sump for my 55DT that is currently only sectioned with baffles to split my skimmer and mag7 return pump.

My question is how small a return section can you have? I was going to make another section on the other side for a fuge.

Or would it be better adding a container as a fuge above the sump and leave the 20 alone, Im going to be running a top off from my basement using an mj1200

 

I would suggest using another tank for the fuge. The return section is the area that shows the evaporation from your system. The smaller the section the greater the chance of running it dry and burning up your return pump.

 

I agree even with 2in10 even if you have a top off the bigger the better. leaves a little wiggle room.