WHEN YOUR BETTA FISH FLARES UP AT YOU, it’s not because it dislikes you — it’s just doing what bettas naturally do to protect their territory. Flaring is when a betta spreads its fins wide and gills out to look bigger and more dominant. Here’s why it happens: 1. Territorial Instincts: Bettas are naturally territorial, especially males. They see their reflection, bright colors, or sudden movements as a possible rival. When you come near the glass, they may think you’re another betta intruding. 2.