Deciding to keep German Blue Rams with Bettas can be a risky proposition. Both species are known for their territoriality, especially around breeding times. This could potentially lead to competition and aggression. Moreover, Bettas prefer slightly cooler temperatures, and these German Blue Rams thrive in warmer water, forming a conflict in environments.
That being said, there may be room for cohabitation in a sufficiently large and well-strategized aquarium set-up. The tank should have ample hiding spots and room for each species to mitigate potential territorial disputes. However, closely monitoring their interaction is crucial if they share the same environment because a fight-free cohabitation cannot be guaranteed.