* Temperature: Betta fish prefer warm water, between 78 and 82 degrees Fahrenheit. Goldfish prefer cooler water, between 65 and 72 degrees Fahrenheit.
* pH: Betta fish prefer a neutral pH, between 6.5 and 7.5. Goldfish prefer a slightly alkaline pH, between 7.2 and 8.4.
* Hardness: Betta fish prefer soft water, while goldfish prefer hard water.
* Activity level: Betta fish are typically less active than goldfish. Goldfish are active swimmers and need a lot of space to move around.
* Aggression: Betta fish are territorial and can be aggressive toward other fish. Goldfish are also territorial, but they are generally less aggressive than betta fish.
In addition to these differences in care requirements, betta fish and goldfish have different temperaments. Betta fish are often called "fighting fish" because they are known for their aggressive behavior. Goldfish are typically more peaceful and docile.
For these reasons, it is not advisable to keep betta fish and goldfish together in the same tank. If you want to keep both types of fish, you should do so in separate tanks.