2. How long will it take and what do I do once they are born?
Once you add your fish (4:1, and making sure they are the same species) leave about a 4 week period for your fish to become familiar with their new tank. After about two months after adding your fish (this largely depends on the type of fish in your aquarium, this 2 months schedule is based on guppies/platies/goldfish) you should start to see the belly or bellies, of some of your fish, starting to increase; this is normal! When this happens the female(s) should stay pregnant for about a month or two before releasing her young or laying her eggs into the aquarium.
As the young are born the other fish in your aquarium will eat the young unless you placed the female in a breeding cage prior to her giving birth or manage to catch some of the little guys before the other fish do. Leaving the baby fry in the aquarium without any protection will result in a high mortality rate.
Please note that the baby fry must remain in the tank they were born in via baby net. or you can transfer the baby fry to a another aquarium with a suitable filter and heater if you wish.
3. Extra Notes
Please see the next section, how to care for baby fry.