If you move the female to another tank, there's a possibility you'll break the pair bond, maybe a 50/50 chance. That may be optimistic. If that bond breaks, at best they'll never breed again if you put her back in the tank and at worst the male will not accept her back and attack her, maybe even kill her.
A much better idea is putting a divider (glass or eggcrate lighting diffuser) in the tank so the male and female are separated but can still see each other. They will also sense each others pheromones and stay familiar with each other. This will be less likely to break the pair bond and give you a break from the continuous breeding. Every so often remove the divider and let them spawn and everybody will be happy.
Another possibility is to keep them together and use the 48" x 18" for a culler fish. Something that will eat all the excess fry and dispose of them. My recommendation is an oscar. They'll eat anything. I always keep a culler, usually an oscar, to dispose of any extra fry. If you're not into oscars, another possibility would be something like one of the larger Hemichromis species (H. fasciatus or H. elongatus). One of the smaller Parachromis species (P. loisellei or P. friedrichsthalii) or a giraffe cichlid (Nimbochromis venustus), or any of the other Nimbochromis species for that matter, may also work. You'll find some argument about the suitability of a 48" x 18" tank for all of these, but IME a 75 or 90 gallon is adequate for a single individual of any of the previous species and I'll stand by my recommendation. The 12" SL (length from the nose to the base of the tail) size listed for these two Parachromis and the Nimbochromis species is a max, not an average. Most males of the two Parachromis species top out in the 11" to 12" range for total length (length including the tail) and most of the Nimbochromis top out in the 10" to 11" TL length range, if that. All in all, they're all about the same size as an oscar.
WYite
