- Size difference: Kissing gourami can reach a larger maximum size than goldfish, and may bully or even eat the smaller fish.
- Temperament: Kissing gourami can be territorial and aggressive, especially during spawning season, and may harass or even injure the goldfish.
- Water requirements: Kissing gourami prefer slightly acidic to neutral water with a pH of 6.5-7.5, while goldfish prefer slightly alkaline water with a pH of 7.2-7.8. Mixing these fish in the same tank can make it difficult to maintain suitable water conditions for both species.
- Diet: Kissing gourami tend to be omnivores, and may consume plants or compete with the goldfish for food, potentially causing health issues for the goldfish.
Overall, it's generally best to keep goldfish and kissing fish separately in order to ensure the well-being and compatibility of all the fish in your tank.