Firstly you apply the basic rule of fish keeping. "1 inch of fish needs a minimum of 1 gallon of water." Knowing that a goldfish will grow to around 10 inches minimum you will supply the fish with a suitable sized tank, (minimum recommended size for 1 goldfish is 15 gallons nominal) a water filter is required to remove the toxins that are created by the fish living and excreting in the tank and a suitable and varied diet. You will also need to do regular weekly water changes of around 50%. If you want the tank to look really nice too then I would advise you to light and aquascape the tank with plants and rocks etc.
I don't know except do not put goldfish in the same tank as anything else the other thing will die. I know from experience. :*(
Usually they spawn in the spring but to encourage it usually slowly raise the temperature
You can keep goldfish or reptiles in them. You can also raise feeder insects in them.
No, it lays eggs, and the other goldfish are going to eat them as they are being laid (I know, strange, but natural). If you want to raise young, your must separate them until they hatch.
Goldfish "spawn" they do not get pregnant because they are egg layers and the eggs are fertilised after they are released from the females body. Goldfish will eat their eggs if they can find them, so either the fertilised eggs or the goldfish should be removed once 'spawning' is completed if you wish to raise some of the young. BTW 1 goldfish spawning can produce many thousands of babys.
Well, when goldfish spawn they lay thousands upon thousands of eggs. The male goldfish then sprays a cloud of milt which fertilises the eggs. For a goldfish to only lay one egg which, somehow triggers a male goldfish to release a cloud of milt, is highly unlikely. Truthfully, it is the person breeding the goldfish who chooses how many fish they are willing to raise. Technically, they could choose to only keep 1 goldfish fry but realistically they would not be willing to throw away the lives of so many baby goldfish fry.
Goldfish do not 'give birth' they spawn as a group. There is no need to change anything after they have spawned other than to either move the eggs or the adult fish if you wish to raise of young.
If your goldfish is jerking around a lot its because its being irritated by parasites. To treat this condition raise the salt concentration to 0.3% and treat the tank with an antiparasitic medication (available at the related link below).
Some common breeds of goldfish are: the Black Moor goldfish, the Ryunkin goldfish, the comet goldfish, the common goldfish, the Calico Fantail goldfish, the telescope eye goldfish, the bubble eye goldfish, the pearl scale goldfish and the Oranda goldfish.
No you cannot put a frog with goldfish; goldfish belong with goldfish
The plural of goldfish is goldfish. It is the same as the singular.
Goldfish do not have legs. Goldfish do have fins, although the number of fins will depend on the type of goldfish.