As an option:
When you get the 125 Gal move the Male Jag into it and get a female Jag...
Then leave the Female Dempsey in the 55 gal and get a male Dempsey...
Then you get to enjoy both species and have 2 types of sellable offspring...
But this approach means you need to get the 125 gal sooner rather than later... if your not getting the 125 gal soon I would find a way to rehome the female Dempsey and get a Female Jag...
When you get the 125 Gal move the Male Jag into it and get a female Jag...
Then leave the Female Dempsey in the 55 gal and get a male Dempsey...
Then you get to enjoy both species and have 2 types of sellable offspring...
But this approach means you need to get the 125 gal sooner rather than later... if your not getting the 125 gal soon I would find a way to rehome the female Dempsey and get a Female Jag...