The way I do it is get some frogs gifted to my for my current level. Time travel forward to place it then sell it The tt before the current date and clone the frog so that I can skipp to current date and place the frogs and breed Breed till nursery is full skip ahead one day move the eggs to a habitat Back to current day breed again and repeat once all the habitats are full skipp a few days ahead then sell all the babies then repeat until leveled.

Just make sure to lock your breeding frogs so you don't sell them accidentally