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Guppies struck with mysterious SBD


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Hail and well met!

After a recent success with a pregnancy scare disaster has once again befallen these burgeoning colonies.

Which is to say I found one of my females from a second tank belly up this morning without warning. She passed shortly after I found her and now rests in the garden. Another of the females was lethargic and, quite frankly, swam about like a drunk when stirred. I jest, to make light, however it was comically tragic to watch her still and shift to a 45 📐 before being slowly sucked up in the current and bumbled about. I’ve since placed her in a QT tank for observation and to save her from the Aquaclear 40 tumbling her about.


There’s a level 1 salt dosing in the tank with her, no other medication besides.

40g Parameters:

  • pH - 7
  • Nitrates - 25
  • Hardness - 100
  • Nitrite - 0
  • Ammonia - 0
  • KH/Buffer - 50
  • Water Temperature - 72 F
  • Tank mates: 4 other guppies, 2 mystery snails, ??? blue dream skrimp

The QT tank has slightly higher GH/KH of 70/150.

I’ve held off ordering meds for now as I can’t see any symptoms other than some swim bladder issue and loss of appetite. No rapid breathing, no clamped fins, no distended belly, no sign of injury, etc. The other that passed this morning was in similar seemingly pristine condition.

I’m hoping the lighter current and break from the males give her the space to recover. As she’s not doing well, at least this environment will provide a more peaceful passing.

The other 4 guppies are seemingly fine, flitting about the tank without apparent issue. I will mention that both this unwell female and the other were considerably smaller than the other two females in the tank, both on arrival and in the month I’ve had them. I suspected parasites but never saw the signs such as visible worms or white, stringy waste.

Searching the forums I found other live-bearers with similar situations, so it could be genetic. If so, it is what it is.

If not, I’d like to hear y’all’s thoughts on these happenings, especially if it strikes any of the other tank mates. I’ll be keeping a close eye on the other inhabitants in case there’s another, well, case.

Thank you for the help!

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Sorry about your fish. Many people have been where you are and know the frustration and feelings of responsibility when trying to keep something alive and it doesn't work out.

I don't have an answer for you but perhaps some encouragement. Livebearers can be difficult to diagnose because a lot of causes can have the same symptoms (lack of appetite, wasting, lethargy, shimmying/rubbing against objects). On top of that they can be genetically weak from in-breeding. You can do everything right, maintain stable ideal parameters, run the gamut in the best modern medicine has to offer, and do due diligence in quarantining new fish/plants but still end up with guppies that end up like the one above.

Reading what you've wrote I can see you've been doing your research. If it is a parasitic infection then they are likely too small to see without a tissue sample and microscope. My advice is to try anti parasitic meds like Paraclense(metronidazole) and Expel-P(levamisole) as a prophylactic if you're able to and make sure all new comers get the same treatment in a qt. If you go this route a follow up treatment 3 weeks later will ensure any parasite cysts that hatched are sanitized too.

My tank has just received the first grandchildren from the store bought generation. Presumably they will be genetically adapted to its environment. If so, there should be far less instances of what just happened to your fish. Something for both of us to look forward to I hope.

Edited by Bjorn
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Do you know the source of your guppies?  Commercially bred guppies are notoriously fragile.  I've rarely kept one alive longer than four weeks.  Guppies bred by a hobbyist are generally much stronger.

By the way, are you hoping for fry?  Some varieties of guppy rarely, if ever, eat fry, and others are very bad about it.  As far as I know there aren't any more enthusiastic fry hunters than albino kois, which I believe yours are.  I've had three females and one male in a heavily planted 5.5 gallon tank on my desk at work since November, and I've never spotted a single fry, in spite of the females occasionally appearing very pregnant.

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I’m happy to report that today there’s no more casualties, nor signs of disease. I will remain vigilant!


Congrats on your established colony! I too cannot wait for these creatures to fully establish themselves. It’s definitely a little wearing, dealing with these sick fish though. I’m not too shaken yet! There are still two seemingly healthy and happy pairs so this colony may yet survive - even thrive!

I’m suspecting a genetic component. Albinos are naturally a bit more genetically weak, if I’m not mistaken. On top of that, aside from robustness these fish all look very very similar, unlike the many slight variations between, say, males I see in the other strains I have. I suspect they’re deeply inbred - Deliverance status.

I’ll get some of those medications to have on hand, also some Maracyn… What others would be good to have in the ‘medicine cabinet’ for guppies specifically?


These guppies came from Houston Aqua, along with a few other trios. I believe they are imported, however aside from this little tragedy they’ve all done very well. One day I hope to be a purveyor of fine bred (artisanal you could say!) million-fish, I would be quite pleased if the humble guppy soared in popularity again regardless.

I have heard the same about albino koi, and also that they’re practically blind which I believe with how uncoordinated these lovely little fish have been while eating. My tuxedo koi on the other hand are almost protective of their fry - at least that’s what I like to believe. 

I’m praying for fry, for sure! Hopefully, between the massive tank and the flotillas of water lettuce the younglings will be able to survive. I have seen two fry swimming about the tank over the last few days! Though… I had added some java ferns a few weeks ago, so they may be hitch hikers? I don’t recall seeing any signs of pregnancy in this colony so far…


If needed though, I have no problem with raising up a clutch in a 5 gallon till they can fend for themselves! Thanks for the heads up though - I may just do that from the get go.

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On 5/17/2022 at 9:56 AM, KungFuKoi-ish said:

I’ll get some of those medications to have on hand, also some Maracyn… What others would be good to have in the ‘medicine cabinet’ for guppies specifically?

You already mentioned you used salt.  Guppies have an advantage by being tolerant to salt treatment.

If you have plants or salt sensitive livestock in your display tank you’ll be thanking yourself for having Ich-X on hand considering how common Ich is.

Those and the one’s mentioned earlier will give you a very robust arsenal of meds.

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Thanks again @Bjorn! Next time I want to be ready, as it seems time is of the essence in these situations.

I’m starting to wonder if this was pregnancy related. Due to the size of the tank, the color of the substrate, and the massive tangle of water lettuce roots I hadn’t realized there are at least 4 little fry hidden here and there - and it seems that they’re of two different broods judging by their development. I was just able to get a great look at one and it seems to be an albino koi fry.


I’m pretty sure that’s an albino koi, judging by the eyes and shape. If I’m mistaken I’ll gladly hear it!

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Well, it’s not pregnancy related as I found one of the males dead to rights this morning. I was watching the tank late last night and there was no sign of distress, and the three remaining fish seem totally unfazed. Luckily the meds should be here today, or tomorrow at the latest.

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Update: Almost done with the Paracleanse treatment and, fingers crossed, it seems to have done the trick.

Yesterday specifically was a seemingly good turn, as now the guppies have gone back to exploring the tank rather than cowering under the cover of the water lettuce.

Tomorrow is the recommended 25% water change, I’m wondering if I should run another course of treatment? Or should I wait until symptoms present themselves again?

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