I wouldn't make the return from the sump over the top if you have the chance to get a hole drilled.
Main advantage is the amount of water you can put through a single 1.5" bulkhead vs. a 1.5" bulkhead in an overflow box. The amount of water for the bulkhead will be much more limited. Couple other advantages are that you can do something like a durso standpipe or equivilent to reduce noise of the water falling, you pull off the surface of the water (strainers can too though), and they can be a little safer for things not getting sucked against the strainer and dieing and clogging it up, with an overflow you have a lot more surface area to diffuse the flow, but that is only important if you are pushing a lot of flow, which you won't be if you are using a closed loop in conjunction with the strainers.
There might be other advantages that I do not know about.
__________________
180g Reef Tank
900w 20K MH
100g Sump
25g fuge
50g grow out tank
Manifold closed loop
ASM G6 Skimmer
|