The only monogamous stomatopods that pair permanently are some lysiosquillids (sand-living spearers). With all others, males and females to do not remain together after mating. Tring to maintain a pair in a small tank is asking for trouble, if not immediately, then when one of them molts.
As I have said many times, it is almost impossible to rear stomatopods from egg to postlarvae. I know of only a few people who have succeeded and they had access to live phyto and zooplankton for food and running natural seawater. My only successful attempt started with over 100 4th stadia larval Gonodactylus chiragra collected as they left the mother's cavity. Each was housed individually in a 100 plastic cup. They were fed a variety of zooplankton with additives and the water was changed daily. After a month, two survived and molted to postlarvae.
Roy