A fish tank would work...make sure you put water in it.:D
an aquarium or a fish tank
You should keep the water at room temperature.
None. A single goldfish should have a minimum of 75L. You would be better off keeping small tropical freshwater fish.
Do Goldfish make good Pets to keep? Yes with the right equipment.
You are describing unusual behaviour for goldfish. Are you sure you have 'Goldfish' as in (Carassius auratus)?
Keeping the water clean in your goldfish aquarium will not only make your fish more likely to spawn but will also greatly improve the health of your fish and any potential fry, so yes you should keep your goldfish's water clean for them to spawn.
No, you should only keep goldfish with goldfish (with very few exceptions such as a bristlenose pleco, apple snail or weather loach for example)
yes you can keep your comet goldfish in a goldfishpond.In fact having them in a pond is a good idea, as long as they are not subjected to herons and other predators, because this variety of goldfish gets very large: up to a foot! :)
The cheapest way to keep a goldfish is to keep it in a fish bowl.........as long as the bowl is big enough the fish will be happy there.
Don't take a goldfish out of water.
You should not feed goldfish soup.
They will all eat one anothers young but adults should get along OK. I do not understand why you would wish to keep wild Rudd in with domesticated Goldfish and Orf though.