Size of sump for 40g breeder

[SeaHorse_Fanatic]

Doesn't really matter the size of sump as long as it can hold your skimmer and other equipment. Ideally, I would fit the largest sump I can into the stand. Usually sump is around half the volume of display tank but if you can I would go bigger. Sump adds volume so bigger sump makes your system more stable than a small sump.

For instance, my 165g has a 90g wide sump.