Is your second female swordtail in an actual aquarium or one of those little breeding traps?
Breeding traps are not suitable for female livebearers because the females feel stressed by being trapped in a small enclosure. This stress can cause a premature labour or if the fry are born the female might turn around and eat them as soon as they are born.
If the female is in an aquarium that is at least 18 inches long, then that is fine.
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When moving pregnant fish, try to keep them in water at all times. Use a net to catch them or guide them into a small container of water, then lift them out in the container of water. Being lifted out of the water in a net can put pressure on the babies and cause problems. This is more of an issue with fish that are nearly due to give birth but can affect any female fish that is carrying babies.
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Have lots of plants in the tank, especially floating plants like Water Sprite (Ceratopteris thalictroides/ cornuta). These will provide hiding places for the babies and the female when she is giving birth. The females take shelter in the plants during labour and the babies head straight for the plants when born.
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Female livebearers can carry up to 6 sperm packets in their bodies and they use 1 sperm packet to fertilise each batch of eggs. If there is a male swordtail in the tank with the females, then the females will have the maximum number of sperm packets as well as being pregnant. If there are only female swordtails in the tank and they have been in a tank with males during the last month, they will be pregnant and carrying a number of sperm packets that will be used to fertilise eggs over the next few months.
The gestation period for livebearers is about 1 month and young females will produce small numbers of fry every month. Older females will produce bigger batches of fry but a little less often.
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If the tank is cycled and the filters have developed, you can feed the fish 3 or 4 times a day and if they are full, they will be less inclined to hunting the baby fish in the main tank. However, you should try to get the babies out asap and move them into their own tank with plants and an established filter.
