To have one fancy goldfish you need to start off with at least a 20 gallon aquarium kit. This kit will come with a filter, filter media, the tank, and likely some decor. You also need to buy a bottle of water conditioner, and some fish food so you can begin cycle your aquarium to prepare it for the fish.
Yes, goldfish are very messy. Goldfish need 10 gallons per fish, you actually need a 20 gallon tank or about a 70 liter tank for 2 goldfish. But the small tank will do while they are small, you will need to eventually get a larger tank.
Either a tank or pond of at least 30 gallons is a suitable environment for a goldfish.
Regardless of the type or size of goldfish the minimum acceptable size of an aquarium for a goldfish is 30 gallons. Buy a tank that is at least 30 gallons if you plan to have goldfish. You can comfortably fit 3 goldfish in a tank this size but no goldfish in a tank any smaller. Goldfish are essentially pond fish and need lots of space to swim; they will not thrive in a small aquarium.
They prefer one.
Yes, but your tank size needs to support it. If you mean that a regular goldfish is a long single-tail goldfish, then you need at least a 40 gallon tank just for the 2 fish due to the size potential of the common goldfish. If you mean a regular goldfish as in a round bodied fantail, or perhaps a ryukin, then you need at least a 30 gallon tank for the 2 fish.
Goldfish just need a plain bowl and some plants
Yes, the bigger tank the better. They actually HATE goldfish bowls. (they're not nearly big enough). Goldfish usually need a 20 to 30 gallon tank
Depending on what your sick goldfish has, it will either be specific to that fish, which you should place in a separate tank to treat, or it's something that will spread to other fish in your tank, in which case you will need to treat them all.
HOPE THIS IS HELPFUL
about 10 gal per fish
Actually, I think that temperature is about right for your goldfish. But if you seriously need to, you need to change the temperature of the air around the tank. I suggest keeping it in a cooler room?
no they need at least five gallons each. a thirty gallon tank is a good size tank to keep goldfish in.