fry mysteriously dying...

If it isn't to late, and you're desperately looking for some advice, hopefully someone can help you out.

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Plastic Mac
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fry mysteriously dying...

Post by Plastic Mac »

This last week has not been good for me. Each day I've come home I've had to go through the horrible task of removing dead fry from my tank. The tank is a 36x12x15 and is filtered by an eheim 2224 plus a vecton UV8. It has 8 adults and at my best ever count, 34 fry. Some of these fry were, reaching a good size of about 2-2.5cm yet they are misteriously dying.
I orginally thought it must be the water, but water parameters are fine and have not changed in months, I use 100% ro water with r/o right with a tds of around 300ppm.

As a side note, if it was a water issue I would of expected the smallest fry to be the first to go, infact I'd say on average it's the older ones. Other than that though, the fish as acting as normal as ever, no signs of anything being wrong going by their actions.

So the only reasons I can thing of are:

1. I use round stones in the tank, which allow the small fry to nestle under the edges out of the way of the adults. The tnak oroginally had a sand substrate but after losing a couple of fry i removed the substrate and the losses stopped. However I didn't remove the decor when I syphoned the sand out so there is still a residue of the substrate under each piece of decor in the tank. So each time I syphon the tank now I remove any sand which has been blown out from under the stones and into the open tank area. This was my first assumption, that maybe it was due to the substrate or possibly some excess food which gets caught under the stones and decays, causing problems if the fry eat it.

2. The tank is pretty much maxed out with adults and the 34 fry are starting to hide everywhere in the tank now, perhaps one adult or more is bullying/beating them to death.

On Saturday after having removed around 8 dead fry over the previous few days, I totally cleaned the tank out, moved all the stones and cleaned each one as well as removing any substrate still lying underneath them. By the end of Sunday I had removed two more dead fry.

The only thing which is left is an adult killing the fry? has anyone ever experienced anything like this before?

The other thing is the fry look fine when i remove them, other than one of two having slightly damaged tails and dorsal fins they look perfect, nothing in their mouths or anything which would indicate cause of death...and it literally it's one or perhaps two at most a day. I'm quite baffled.

I'm now off to go have a second tank drilled so i can move the fry to another tank but keep it all on the same system. However I'd really appreciate anyones thoughts or ideas as to what it might be.

cheers
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Post by dave »

Just a guess.

The fry that are older are becoming territorial and competing with each other.

Another member PM'd me with the same problem in the same size tank, 30 plus fry and no adults. The older fry were the ones that were being killed. Similar sized fish are likely to continue the rivalry a lot more.

I think it unlikely that young would compete with adults, as no competition.

In order to avoid this I build my tanks up with Mopani Wood so that the territories are not just on the base of the tank, but extend upwards.

Hope this helps and good luck

Dave
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Post by McEve »

Territorial fights shouldn't occur until the fry is about 15 months old. Before then they have no need of a territory but rather stay with the group bickering and practizing their territorial abbilities.

I did have one adult male that killed fry. But he hadn't stayed with the fry as they were growing up (actually he attacked grown females as well), so I seriously doubt there's an adult killing your fry.

However, there are two options I see as possible culprits, others might see other though.

1. You've got a bacterial infection going. I was called upon by a fellow breeder in Norway that experienced mass death without seeing any obious reason for it. Esha2000 stopped it for him. with some ado I got EshA200 to him. He sendt me flowers after that :D

2. The tanks is overcrowded? I assume you have checked the parameters of the water so I won't go into that here. If however you find the fry dead at the same spot you might have, as you mentioned, contaminated sand in the tank still, which is suffocating the fry if they decide to rest at the wrong place.

Good luck and let us know how your doing!
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Post by Shimmy »

I have had the same problem as dave has mentioned and I can only think that it is a bacterial infection or territorial dispute hence I was asking the question as to whether there is any limit to keeping fry together. Why is it though tha it is the older fish as apposed to the young fry if it was bacterial wouldnt it effect the weakest first?

I am as eager as Plastic Mac to get answers on this????!!!!!! :(
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Post by McEve »

it depends on what age you call fry. If you have a look at my babycam you'll see 28 fry, ranging from 5 to 8 months. They have no trouble with territory, no disputes with the adult fish.

I do however remember that when the other breeder experienced mass death, it was indeed the older fry that went first, but not only them.

I don't know why, speculating in the older fry, in an overcrowded tank, getting less food then they need, and thereby being more suceptible to infections?

I don't know. I can only report what I've seen happen before :?
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Post by Raul-7 »

Interesting topic, although probably heart-wrenching seeing them die without a possible reason.

Do you run your UV sterlizer 24/7? I have heard that running it 24/7 can weaken the fish's immune system as they gradually (overtime) lose their ability to fight off viruses, parasites they would normally encounter in the wild.

I assume the adults are more resistant since they obviouslly lived in an unsterile environment before you got them but the fry are very susceptible since they are still very young and their immune systems haven't properly developed. Maybe there's a UV-resistant virus or bacteria infesting your tank? I know they die on UV contact, but maybe it has attached itself to the glass, decor, etc.

Just a possible theory.
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Post by Plastic Mac »

Thanks for the replies guys,

@Dave,

I don't think its territorial between the fry as so far I haven't seen anything more than what McEve suggested ie. 'staying with the group bickering and practising their territorial abilities'. I would of also expected to see more damage on them if it was from another fish the same size, as it would have been a more 'even' fight I'd of thought. This is why I assumed the culprit would be more likely to be an adult, as one or two of the adults in the tank have to spend most of their day surrounded by 10-15 fry constantly moving and bickering around them.
I may well try the mopani/bogwood and see if that makes any difference. Although I've just got back from having a second tank drilled, and having booked a day off on wednesday I should hopefully be able to transfer all the young ones into the second tank and solve the problemm, assuming that's what the problem is.

@McEve

A bacterial infection is a possibility, although I'd be very surprised if it was, as imo a bacterial infection should progressively get worse within a closed enviroment but instead it seems to be running as a constant, never more than one fry a day from what I can see. Along with the fact that a uv is running on the tank as well, then like I said, i don't think it is. If however nothing changes after moving the fry to the new tank then I wil certainly give that idea more thought.
As for your other idea, then yes I do think the tank is now overcrowded and you do also bring up another very interesting point. I seem to be removing the fry mostly, if not all, from the left side of the tank, which is made all the more interesting by the fact that 20 of the 34 fry used to, until I did the major clean on saturday, live under a piece of slate on the right hand side of the tank. In which case you could well be right about the residual traces of substrate under the rocks being contaminated.

@Raul-7

Yes I do run the uv 24/7. I think your kind of right in your assumption of uv but coming at it from a slightly wrong direction imo. A uv will not weaken a fishes immune system as such, what it does do is prevent a fishes immune system from improving. In short, by killing all the bacteria, a fishes immune system doesn't get to fight the bacteria and learn to combat it. However, your argument may be correct if a uv light is used through several generations of successive spawns.
and yes you're right it is heart wrenching but I'm hopeful it'll be over soon without too many more going.

Thanks for the replies so far.
Plastic Mac
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Hi

Post by dave »

Rob wrote:Hi Ken

I think dave has hit the nail on the head. I was thinking that you were talking about vey young fry.

Squabbling will probably be your answer.

The younger fish do not compete to well against the older. so the gap between the 1 month and 5 month may just be a little too much. Is there any way that you can segregate the tank, i.e perspex with holes drilled in it?

rob
I'm not sure what the answer is, but I do believe that territoriality is exhibited in young fish, and considering the number of fish in the tank, and how many hiding places could be a more determining factor.

While the above quote refers to younger fish suffering, and I have witnessed serious squabbling between young of 5 or 6 months old and the addition of more hiding places solved this problem.

Dave
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Post by McEve »

Just to avoid confusion, make sure it's clear what thread you're quoting from.

Quotes possibly taken out of their context might be confusing :wink:

You are of course welcome to take a look at the babycam (in the menu under "home"). There's three spawns growing up together, ranging from 4 to 8 months, the youngest grew up together with the oldest.
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Hi

Post by dave »

The thread quoted fom was started by Ken 4 August 2006, with fish between 1 and 5 months old.

My experience was with 30 plus young in 4' x12"x15" and no adults, 5 to 8 months old.

Shimmy mentioned earlier in this thread a loss of fish ( Reason Unknown ).

I really do not know what the answer to Plastic Macs plight is, but my feeling is that there is some territoriality in young fish. And while their habit of congregating in groups under lean toos indicates otherwise. Providing the wood provides additional hiding place for the fish that are evicted from these gatherings.

My thoughts from my experiences were offered so that together with your ideas, Plastic may be able to resolve the situation.

Dave
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Post by McEve »

I apreciate your intentions and good intent. All I asked for was a link to the thread when you choose to quote from another thread :)

Actually, I expect it, as to not confuse matters
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Post by Barbie »

Is it possible that they are choking on the food? I've found that the fry sometimes reach a certain age where they can suddenly eat entire pieces of food that they were having no problems with when they could only gnaw off small pieces. A friend just recently lost 3 fry that way. It's far fetched, but I thought I'd check. Do the fry show any symptoms? Besides being suddenly dead I mean?

I've kept a pretty good number of fry in bare bottom tanks with minimal decor with no losses. I really can't see fry that size having THAT much of an aggression issue, personally.

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Post by alevans »

Hi

I subscribe to the choking theory too. I lost all bar 3 from a spawn, whilst trying to 'experiment' with what they wanted to eat. I now use large pieces of algae wafer which can only be sucked/nibbled at and not swallowed whole. So far so good.

Good luck
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Post by Plastic Mac »

Yes I think that could be a possiblity, but it did occur to me (having remembered your bloodworm story Barbie) so I hadn't fed anything other than catfish pellets (like Alevans stated far too big to be eaten whole), daphnia, baby brineshrimp, cyclops, red plankton and nothing else since the first one died. The only item which I think could possibly be the problem is maybe the daphnia but I wouldn't have thought so, unless you think differently. I did also check their mouths and although I didn't look under a microscope or perform an autopsy I could see no signs of any blockages.

Fingers crossed, since I did a major clean, removing every last bit of substrate from under the rocks, I haven't had a death since sunday. It's a little to early in my opinion to say that was the problem, however there is a little ray of hope there I think.
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Post by alevans »

Dom

I pleased that you have had no further deaths. When it happened to me I did conduct an inspection of the dead fry and there was a blockage, but a bit further down, i guess in the throat rather than the mouth. It's so difficult to tell on something so small.

Just as a final thought, were the dead fry of normal shape? If they were 'fat' it can indicate a catastrophic liver failure which can be caused by high nitrates (above 50 mg/l). I'm guessing that by using r/o that isn't the case for you, but I thought it would be worth a mention.

Good luck.
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