You have several choices, get a larger tank for them or put them into a pond (where goldfish should be) or remove some and take them back to a pet shop. Whatever you decide to do is up to you. You may even be able to think of some other alternatives.
They don't, the lack of space and oxygen will kill them..just like any other fish.
If you buy a feeder goldfish, usually their lifespan isn't that long, because they are eaten by another pet animal soon anyway. However, I doubt that their lifespan will not be so different from a normal goldfishs' if you take care of them properly-just like a normal goldfish. It is just that they are normally sold in such crowded spaces that I think they are more prone to disease.
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.
Crowded
The comparative form of "crowded" is "more crowded."
No you cannot put a frog with goldfish; goldfish belong with goldfish
Yes. "Crowded" can be a verb (as in "People crowded the stadium") or an adjective. (as in "The stadium was crowded because of all the people.")
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.
Goldfishes There is no plural for goldfish. Goldfish itself is plural. Example: Hey Bob, can I see that goldfish you caught? Example2: Hey Bob, can I see those goldfish you caught?
there are three basic breeds: fantail goldfish, comet goldfish, and common goldfish. if you are getting goldfish for the first time, i would recommend common goldfish as they need the least care.
10 / 15 = 66.7 % 66.7% of 15 goldfish is 10 goldfish