Disappearing Fry?

[katelyn7014]

I'm not sure what's happening to my angelfish fry. They're in a 10 gallon tank all by themselves, with a filter that has nylon over it, and of course a heater.. and that's about it. I started out with 11 wigglers, and last week I could only count 8 or 9. Today I can only seem to count 5. I'm also really careful with my water changes, making sure not to get any of the babies.. I always double check. So I'm not sure how the number is dwindling without me knowing how..... Any ideas?

 

[Fishobsessed7]

They may be dying


Fishobsessed7

 

[katelyn7014]

Yes but I haven't seen any dead bodies of the fry in the tank... I thought I would see them floating in the tank if they had.

 

[Andy Sager]

The fry will eat each other if one dies. Also, they may be getting sucked up to the nylon and disintegrating into the filter before you notice. This is why sponge filters work better for fry than other filter types. Sponges will not suck up a fry because they are air driven and the fish can swim away from the current.

 

[katelyn7014]

That might be what's happening... It's just funny that I haven't even noticed any little lifeless bodies floating in the tank if they were dying. I have one of the Tetra Whisper filters in that tank with the nylon over it, that might be what has happened. Whenever I've watched them they never seem to get near the filter or if they do, have any trouble around it.. but I can't think of any other reason of what might be causing the disappearance. If I have a next batch I'll most likely look for a sponge filter instead of using a nylon.

 

[Andy Sager]

You just can't beat an air driven sponge filter for raising fish fry. It is pretty much fool proof and harmless to the fry. I don't breed any fish without one ( except anabantids, they don;t need any filters )

 

[jlk]

My suspicion is cannibalism. Although I do not raise angels, I have watched a spawn of 800+ goldfish fry cut down to less than 200 in under a week despite being fed 8-10x a day. Mother nature unfortunately can do quite a job culling fry even if you not wish it to happen. Separating the largest fry from the group has had the most success in my case. Perhaps this will be of some benefit in your present situation or in the future.


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[katelyn7014]

Thanks, I didn't even think of that. I thought that wouldn't be an issue where they were all under 4 weeks old... This was happening over the span of those 4 weeks... How old would you recommend to start dividing them?

 

[Andy Sager]

Thanks, I didn't even think of that. I thought that wouldn't be an issue where they were all under 4 weeks old... This was happening over the span of those 4 weeks... How old would you recommend to start dividing them?

Unfortunately, over the course of those first few weeks, fish fry die for a number of reasons and there is not a lot you can do about it. Some of it is just natural selection. You will need a lot of tanks to start separating fry that grow that millimeter larger, faster than their siblings and it can drive you crazy.
Cannibalism also doesn't mean that the fry were alive when eaten. It's just why you couldn't find the bodies.

For me, a successful spawn is when I get about 100-150 fry to selling size. If you think about it, that's about 30% or less of a spawn. That's because there are a number of natural factors that effect the fish. There is a formula that states that in animals with multiple offspring at a time, only 1% of those offspring make it to breeding adults. That means that for every 100 babies, only 1 is designed to make it. What we as aquarists do is make those odds a little better because we eliminate the predatory aspects of fry loss by other animals or fish. So, if you think about it, 30% is a good result.

Unless there is really a large size difference, I don;t separate fry until they are about 4-6 weeks old ( when they are moved to the grow out tanks.) At that point, it can be helpful to split the sizes so that the smaller fish have a better chance of getting food and not getting picked on by their larger siblings. Again, this requires more tanks or 1 larger tank with multiple dividers.

For now, I would switch to the air driven sponge filter and prepare for the next spawn. Hopefully, you will have a larger amount of fry to work with so the loss of a few will not be as noticeable.

Hope this helps

 

[fazal]

You should use a sponge filter instead of a power filter...the filter could be pulling them up as soon as they die...

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[jlk]

Always great advice, Andy!

Once again, I will stress this is my experience with goldfish fry. If I do not start separating them by size by the second week, the largest fry will eat the smaller fry. Not dead smaller fry, but actively chase down smaller fry and eat them alive. It's actually quite disturbing to witness. The smallest fry I normally cull anyway, so this saves me from the task.

However, in my experience, the largest fry need to be separated as soon as possible (when there is a visual difference in size) as they will continue their relentless pursuit of those that may (or may not at first) fit in their mouths. Basis of natural selection/survival of the fittest. Ironically, my bad cannibals are almost always in the top specimens I have remaining after starting with a huge number of fry.


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[Andy Sager]

Always great advice, Andy!

Once again, I will stress this is my experience with goldfish fry. If I do not start separating them by size by the second week, the largest fry will eat the smaller fry. Not dead smaller fry, but actively chase down smaller fry and eat them alive. It's actually quite disturbing to witness. The smallest fry I normally cull anyway, so this saves me from the task.

However, in my experience, the largest fry need to be separated as soon as possible (when there is a visual difference in size) as they will continue their relentless pursuit of those that may (or may not at first) fit in their mouths. Basis of natural selection/survival of the fittest. Ironically, my bad cannibals are almost always in the top specimens I have remaining after starting with a huge number of fry.
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That's just it, not all fish raise the same way. Goldfish (a.k.a. Carp) are very different from Angelfish. I used to breed them too (when I lived in NJ) and what an issue it was having enough space indoors to house all the different sizes from 1 spawn. lol Runts became Oscar food quite quickly.
Thankfully, Angels are not as aggressive and size differential is not as high in the beginning. It's only after they start looking like little Angels that they start acting like little devils

"If I do not start separating them by size by the second week, the largest fry will eat the smaller fry. Not dead smaller fry, but actively chase down smaller fry and eat them alive. It's actually quite disturbing to witness." This only reiterates that breeding and raising fish is not for the squeamish. It can be brutal, but it's nature at it's most natural. If all offspring survived, there would be no place for them all on Earth.