The term "demo fish" isn't a standard term in ichthyology or aquaculture, so it might be a misunderstanding or a specific reference in a particular context. Here are a few possibilities for what it could mean:

1. Demonstration Fish

• In Aquaculture or Marine Biology: It might refer to fish used for educational or demonstration purposes. For example, fish might be used in demonstrations to teach about aquatic ecosystems, breeding, or fish behavior.

2. Demonstration Species

• In Aquariums or Educational Settings: Certain species are commonly used to showcase particular traits or behaviors. Examples might include:
  • Betta Fish (Betta splendens): Known for their vibrant colors and aggressive behavior.
  • Clownfish (Amphiprioninae): Famous for their symbiotic relationship with sea anemones.