hi ive just recently bought 2 female and 1 male halfbeaks and i jus need to no how to tell if their pregnant, how long they take before they give birth, how many babies they have, how to get them to breed often.
I've got information and a breeding diary on halfbeaks here. But just to put this in context, halfbeaks are not like guppies. You can't make them crank out babies. Just doesn't happen. There also seems to be a sharp decline in fertility once the females get older. For some reason you tend to get a few broods per female, and then nothing. This may or may not be related to diet.
The main trick to breeding halfbeaks is to fill the tank with floating plants. The fry will hide there. The parents aren't especially predatory. You scoop out the fry and rear them in another tank. Expect around 10-20 fry per batch, but a batch can be much smaller. The fry are quite easy to rear.
Your main problem is ensuring the female doesn't miscarry. Many things will cause her to miscarry: shock, water chemistry changes, the wrong diet, aggression from other fish. Never, ever put a female halfbeak in a net or breeding trap.