It sounds like your fish has an infection, it may be bacterial. Go to a good aquarium store and get a broad spectrum antibiotic, triple sulfa is a great one, make sure you follow the directions carefully. As well as this, adding rock salt to your fishes water will help it to recover and prevent it getting sick again, 1 teaspoon per 10 litres of water.
Not particularly. Black Moors are Goldfish. They are not schooling fish. Each goldfish needs at least 10 gallons of water so if you want to keep a few of them you will need a large tank.
If it is as old as a goldfish that can, it can.
When goldfish are large enough, they are called carp. Tilapia is not a goldfish or a carp, although the species does have some similarity.
Goldfish need to mature before they can lay eggs and they can get pretty large (6" or more). By the time they are large enough, they have outgrown a fish bowl. So technically, the answer is no. You will need large goldfish in a large tank before you can breed them.
No, this is because a goldfish and a clown loach are not compatible and should not be in the same tank. One clown loach needs a 75 gallon tank on it's own as they grow very large. In addition, a clown loach needs warmer water than a goldfish.
large fish.
Grams.
Koi
When the pupils on a goldfish are very large and dilated, this can mean one of two things. The fish could have a parasitic infection or a bacterial infection.
No, Goldfish belong with goldfish with a few exceptions such as weather (dojo) loaches, apple or mystery snails, or bristlenose plecos; but only if you have a large enough tank.
Guppies don't get large enought to eat goldfish. They will eat anything they can fit in their mouth. The goldfish might eat your guppies though.-Melchisedek
Yes, the rate at which a goldfish grows, and its overall size, is often partially determined by its environment. This is why pond goldfish are considerably larger than aquarium goldfish, and why goldfish that are cramped-up in bowls stay relatively small. If you want your goldfish to grow into large healthy fish you'll buy them a large aquarium or pond to live in.