Fry staying on top of tank

slwilson8

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I brought home a pair of balloon mollies a couple of days ago. I could see that the female was about to pop when I got her home. By morning I noticed the first fry. I've had a lot of fish over the years and a lot of fry, but these are totally different. I walked away for a few minutes and by the time I got back there were like five or six fry, but they were all on top of the tank. I've never seen them do that before. Also, they seemed really large for just being born. Normally I've only seen them hiding in the rocks and they were a lot smaller and as they got older I would see more and more but they were still all hiding in the rocks. It kind of scared me. I caught as many as I could and separated them from the others but my question is, is this normal? It's been two days now and there are continually a few at the top.
 

GFAJ

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If they seem to big It is possible that they were born a couple of days back and have started to come out more. Other than that it could be a lack of oxygen but quit unlikely unless you see them gasping and trying to ripple the water surface. Have you ever had baloon molly fry again?
 
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slwilson8

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If they seem to big It is possible that they were born a couple of days back and have started to come out more. Other than that it could be a lack of oxygen but quit unlikely unless you see them gasping and trying to ripple the water surface. Have you ever had baloon molly fry again?
 
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slwilson8

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They were just born that day, I just got the fish the night before. They were the first fish I put in the tank.
 
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slwilson8

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Thank you. I had never seen that before so it worried me. But I’ve also never seen them born that big either. If I hadn’t known for a fact that were just born I would have thought they were a week or more old.
 

AdoraBelle Dearheart

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I have guppies, mollies and platies who breed, and it's normal to me for fry to gather at the surface when newborn. Many of them stay in the plants I have there and only dart out to grab food until they're large enough not to get eaten. I advise new people with livebearers to have some kind of floating plants for them to hide in for that reason.

Sometimes a few will head for the bottom instead and hide among the substrate and plants, but in my experience, most go to the top.

Can't explain why they're larger though! Perhaps she had a smaller batch of eggs this go round, and the fry had plenty of room to develop? Just a hypothesis though. Congrats on your fishy babies :)
 

emeraldking

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Thank you. I had never seen that before so it worried me. But I’ve also never seen them born that big either. If I hadn’t known for a fact that were just born I would have thought they were a week or more old.
With ovoviviparous livebearers as yours, we're dealing with pre-fertilization. This means that before any mating will take place and of course naturally before a fertilization (if the female opens up one or more of her fallopian tube's {= uterine tube} folds to let one or more sperm packets fertilize the eggs) takes place, the female already takes care that the eggs will be provided with sufficient nutrients. The developing embryos will be fed by these nutrients only. If the eggs are overfilled with nutrients, those embryos will become larger in general. But also when a female has a longer gestation period than norma, the newborns can be larger. And sometimes there are less eggs than the average number which gives the opportunity to let the embryos grow larger within the same gestation period.
 
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slwilson8

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With ovoviviparous livebearers as yours, we're dealing with pre-fertilization. This means that before any mating will take place and of course naturally before a fertilization (if the female opens up one or more of her fallopian tube's {= uterine tube} folds to let one or more sperm packets fertilize the eggs) takes place, the female already takes care that the eggs will be provided with sufficient nutrients. The developing embryos will be fed by these nutrients only. If the eggs are overfilled with nutrients, those embryos will become larger in general. But also when a female has a longer gestation period than norma, the newborns can be larger. And sometimes there are less eggs than the average number which gives the opportunity to let the embryos grow larger within the same gestation period.
That makes sense. I know when I brought here home that day she was huge! I could tell she was about to pop but I had never had a balloon belly have babies before so I just assumed that’s why she looked so big.
thank you
 

Colin_T

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Most baby fish normally live just under the surface for the first month of life because that is where the plankton is (within the top 2 inches of the surface).

In an aquarium if there is no surface plants, some fry will move down to the bottom to hide among ornaments or plants at the bottom.
 

FishBearer9845

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Does that rule of thumb follow for all fish? If you’re unsure, just check the directions of their mouths and the location within the tank (top, middle or bottom)??
 
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