For Goldfish:
* Aggressive and territorial fish: Goldfish are relatively peaceful, but they can be nippy and territorial, especially when it comes to their food.
* Cichlids: Many cichlids are too aggressive and can bully or injure goldfish.
* Loaches: Some loaches are territorial and can be aggressive towards goldfish.
* Barbs: Some barbs are known for being fin-nippers, which could harm a goldfish.
* Gouramis: Dwarf gouramis are peaceful, but larger gouramis can be aggressive towards goldfish.
* Fish with different water conditions: Goldfish need cooler water temperatures than many other tropical fish.
* Most tropical fish: This includes fish like neon tetras, angelfish, and discus.
* Fish that are too small: Smaller fish may be eaten by larger goldfish.
* Neon tetras: Even though they are peaceful, goldfish may view them as food.
* Snails: Goldfish are notorious for eating snails, which can be frustrating for snail enthusiasts.
For Bettas:
* Aggressive fish: Bettas are known for their territorial and aggressive nature, particularly towards other males.
* Other Bettas: Male bettas should never be housed together.
* Cichlids: Many cichlids are too aggressive for bettas.
* Fish with different water conditions: Bettas require warm water, while some fish, like goldfish, need cooler water.
* Fish with flowing fins: Bettas may nip at the fins of other fish, which could harm them.
* Guppies: While guppies are generally peaceful, their flowing fins may attract a betta's attention.
* Angels: These peaceful fish can be vulnerable to betta aggression.
* Fish that are too small: Bettas may view smaller fish as food.
Some good companions for goldfish:
* Other goldfish (of similar size)
* Some hardy, peaceful species:
* White Cloud Mountain Minnows
* Rosy Barbs
* Platyfish
* Swordtails
Some good companions for bettas:
* Dwarf Corydoras catfish
* Ghost shrimp
* Snails (like Nerite snails)
Important Considerations:
* Tank Size: The tank size should be large enough to accommodate the fish and provide ample space for swimming.
* Water Parameters: All fish should have compatible water parameters, including temperature, pH, and hardness.
* Observation: It's crucial to observe the fish carefully for any signs of aggression or stress. If there are issues, it's best to separate the fish.
Always research the specific needs of the fish you want to keep together and ensure they have a compatible environment before introducing them to the same tank.