Hello Gianne,
What Peter Finke says will happen if you have enough hiding spaces, beechleave or oakleeves will help them also, I leave these in until they are totally gone. Next to Javamos or peat, that will also work. I have 3 pairs and they spawn regularly, I also tried the snatch Methode but found out that they wouldn’t breed anymore. Linkei Larve wil not get black, but will stay light like bettafry 🙂
Hope this helps. 😉