Help! Pointed tail guppy babies

Hello, my guppys had babies and i move some of the babies to a smaller tank so they wouldn't be eaten, two weeks later I saw in the main tank some babies developing very well that were hidden before. At the same time in the smaler tank they waren't developing and started closing their tales like needles, so in order to prevent all babies from dying I moved the ones still open to the main tank but one week later they also closed their tales... what is happening and should I take them out? Will they "infect" all the other good ones? I don't want to lose all of them
Sorry for my bad english,

I have a guppy/shrimp tank and so far my guppies do not appear to eat their young. I started out with 8 adults about 3 months ago and have over 30 young not counting another band new litter just arriving yesterday, I have not seen their tails do this but they are very tiny.

Retired Viking said:

I have a guppy/shrimp tank and so far my guppies do not appear to eat their young. I started out with 8 adults about 3 months ago and have over 30 young not counting another band new litter just arriving yesterday, I have not see their tails do this but they are very tiny.

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Thanks for replying, I took them out cause I saw them eating them right after their born... I will take a picture of some that have a closed tail and all of the other died as soon as their tail closed

They look like swordtail guppies.

Deanasue said:

They look like swordtail guppies.

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But he had a nice open tail before this..

I did some research and it is not uncommon for guppies to eat their young, my guppies apparently do not know this. I have watch newborns swim right in front of the adults and they just ignore them. I must be feeding them the right food. As far as the tails go many call it needle tail and it is a genetic defect. Most fry die with it.

Retired Viking said:

I did some research and it is not uncommon for guppies to eat their young, my guppies apparently do not know this. I have watch newborns swim right in front of the adults and they just ignore them. I must be feeding them the right food. As far as the tails go many call it needle tail and it is a genetic defect. Most fry die with it.

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Ohh thanks , you think is better to move them for another tank? I'm afraid the others can be sick too

According to what I read it is not a diseases but a birth defect possible from too much inbreeding so the other fish should be alright

it's caused by poor water quality or an external protozoan infection.

do big daily water changes and gravel clean the substrate.

add some salt.