One goldfish requires at minimum 20 gallons on it's own plus 10 gallons for each additional goldfish (30 gallons for 2 goldfish). It's not only because of how big they can grow, but because they are very messy fish & produce a high amount of waste
Yes.
not better in groups
Normally goldfish are peaceful and calm.But incase your goldfish is doing so then its better to separate the new goldfish.
It depends, if the goldfish are all males (or females) no, but if not of course they can mate.
Yes. It should be fine. I have 2 regular goldfish living with a bubble eye goldfish and to fancy fantail goldfish, so I think it will be okay.
Yes, goldfish can survive without food for two days.
The answer is no. People usually think that goldfish get lonely and depressed. This is not true. Goldfish are fine on their own! People usually prefer 2 or more
no. i have had two big comet goldfish with my, little 2 inch fish, and they never ate him.
cause it can breath better
That is a matter of personal preference. Read the ingredients on the label and make your decision based on the higher the amount of protein the better the food is for goldfish.
It is recommended to have at least 20 gallons of water to house 2 goldfish.
cold is better cuz when your in the ocean is the water hot or cold cold