When they start having offspring.
Extremely variable by type of fish.
i dont exactly know how to anwser this but fish and rats tend to breed every quickly and rappitly
they have white spots on them when they want to breed. NO YOU CAN'T MAKE THEM BREDD LET THEM DO IT ON THERE ON.
Provided the fish has been reared properly, a goldfish is usually mature enough to breed at about 2 years old. You will only know if it is mature enough during breeding season (spring time) when the females get chubby tummies and the males develop white spots on their gill plates when they come into breeding condition.
Maybe they do and you just don't know it.
If the fish is more red than orange it could be a red wag swordtail or even a platy. well... male- all orange with a line of black on the under side of the tale is a xiphophorus helleri swordtail from the southern mexico, Guatemala
no Edit: Whoever answered that doesn't know the game. Yes, you can.
well im not entirely sure but i don't belive any freshwater fish are easy to breed. I would not recomend breeding fish unless you do the proper research. you have to know what your doing. if you already did your research the find a breed that you like and breed um up.
You can only tame an ocelot with fish and it the only why to breed cats (as I know of.)
the males have a sword like tail and females dont.
all you really have to do is put a boy and a girl in a tank together and before you know it you have mini mollies and when its does happen take out the bigger fish because they will eat the little fish
# Marine-The marine fish have to have saltwater these fish would live in the reefs. # Coldwater-Goldfish fantails (I have these) the normal goldfish. These are other type of coldwater fish- clam,plec and mountain minnows. # Tropical-These fish come in a range of colours and types including pink glass fish,plec,tetres,parrot fish,silver dollars,guppy and shrimps there is many more. # Pond Fish-Simlar to gold fish but live outside in a pond it is a good idea to cover your pond with chicken wire so no birds can eat your fish. I think that it would be a good idea if I tell you the guppys (tropical fish) breed easily.The males have a fancy tail where as the females have normal tails. if your fish do breed it would be a good idea to get a net that goes in your fish tank so no other fish eat your babies.Also the swordtail breed easily the males have a sword like tail and the females have a normal tail. I thought you might need to know this just in case it does happen.