swords3711

Here is what happened
I have a 35g with a filter and an airstone. Out of the ten or so different swords I have had, I have had three last over a month. None of the ten had ever been pregnant. The water checks out just fine.
I did have a strong current and other fish in the tank.

When I reestablished my 10g tank, I bought a pair of mickey mouse swords and eventually a pair of red swords. There is a cory and no air stone to add more air to the tank. Both females are pregnant and none of them have even shown signs of illness.

Just a theory I have composed: Swords like more settled water and to be by themselves with other swords.

Chief_waterchanger

Actually,

They are probably breeding and having fry, but the fry are probably being eatten before you see them. Are you using "swords" to describe both swordtails and platies? Platies are not swordtails, both are from the Xiphophorus genus, but different species. The gestation period is 28-32 days, if that happens to fall on a day you are at school or otherwise absent from the tank to check throughout the day, you could miss the whole load of fry.

It is just not a sound assumption that sexually mature females have been in the tank with sexually mature males and not been impregnated. Swords, platies, mollies, guppies, and endler's livebearers are pretty much constantly pregnant if in mixed gender tanks and are sexually mature.

Good luck.

swords3711

Swords is just refering to "sword"tails. Not platys. My platys and mollies are constantly reproducing. My guppies have gotten fat but never produced anything that I've seen in time. But for my swords, I had a pair of red swords and a pair of red wag swords. The red swords were in my tank together from july to the beginning of december when my male sadly died of old age. The female never increased in size and the male never even showed signs of intrest in her.
My wag female was pregnant when I got her. She contracted popeye. I quarentined her where she gave birth. The fry were lost and the male died in the tank before I could return her to the tank.

Chief_waterchanger

Swordtails are like all other members of the Poeciliidae family of fish; the females can store sperm for upwards of 6 months to reimpregnate themselves at will for that period of time, even without the presence of a male. That's why they tend to stay constantly pregnant, the males refill them with sperm, and they continue using up the older sperm mixed with the newer sperm.

As far as not catching the fry before they are eatten, I would try dense surface and midwater plants. Water sprite and guppy grass/java moss in thick thick thick blankets work nicely for us.

Good luck with that.