5 Fish Dead In One Day

DutchAquarium · May 10, 2018

Could you post a picture of your fish, maybe we can see something on them.

Jenoli42 · May 10, 2018

I'm very sorry for your losses

Hmmm... there are quite a few variables that may have lead to this if i'm reading your post correctly:

1. swapping out the old filter for a new one. did you keep all the old media and put it in the new one, or just have them running side by side? if it was running side by side for 2 weeks, i would personally have done at least a month. remember, just because you get a new filter doesn't mean your bacteria double in size. it means some bacteria move out from the "city" (old filter media) to the "suburbs" (new filter media). that's probably why you're seeing nitrite. having said that, assuming you tested daily since you took out the old filter and your levels never went about about .25, then prime SHOULD have kept your fish safe.

2. medication....sorry i don't know enough about using meds but i have read that some meds can harm healthy fish? someone else will need to comment. other meds can hurt your cycle. i have no idea about myaxin but i'm sure you did your research so this option is less likely.

3. adding new fish without quarantining them. who knows what they brought into your tank and if one of the new ones already died, this option is a front runner. did you acclimate them before you added? any symptoms before it died?

i hope some of this is helpful in figuring out what's going on here...

Trott · May 10, 2018

Is it possible your tank went through a mini-cycle after switching filters? If the tanks mature having any nitrites might be a sign somethings happened with the media. Are any of the other fish behaving oddly? Lethargic, hiding or red gills? Dropsy due to old age is possible but it may have been a sign that your tank re-cycled and the older fish were more vulnerable to the ammonia/nitrites. Mystery fish deaths are tough to diagnose without any symptoms/pictures.

Another possibility is the new guppy brought something with them. If the three have only been in the tank for two days they may not be showing symptoms yet, but it may just be the stress from transport that claimed the first one. I'd keep an eye on them for changes.

Edit: Jenoli types faster!

Jenoli42 · May 10, 2018

Trott said:
Edit: Jenoli types faster!

Great minds think alike, mate! I have the edge when i'm on my laptop indeed

i totally agree with your insights i hope we can help the OP because seeing dead fish when you look in your tank is a horrible feeling

ParrotCichlid · May 10, 2018

Trott said:
Is it possible your tank went through a mini-cycle after switching filters? If the tanks mature having any nitrites might be a sign somethings happened with the media. Are any of the other fish behaving oddly? Lethargic, hiding or red gills? Dropsy due to old age is possible but it may have been a sign that your tank re-cycled and the older fish were more vulnerable to the ammonia/nitrites. Mystery fish deaths are tough to diagnose without any symptoms/pictures.

Another possibility is the new guppy brought something with them. If the three have only been in the tank for two days they may not be showing symptoms yet, but it may just be the stress from transport that claimed the first one. I'd keep an eye on them for changes.

Edit: Jenoli types faster!

Just my opinion but i doubt this has anything to do with the filters or a mini cycle of any kind.

If the cycle had crashed to a level that would kill this many fish it would show on the water test. Parameters while not perfect are not the worst either. I find it hard to believe that 0.25 nitrite is enough to kill 5 fish on the same day.

Unfortunately i can not be of much help past this without seeing pictures of the fish but i would be more inclined to think towards an internal bacterial infection or parasite. Not all are visible on the outside of the fish.

Brannor · May 10, 2018

Been there... we've lost 7 of our 16 guppies we had during our cycle - finished about 2 months ago... I've watched (for the < 30 minutes) them actually go from healthy to dead... without knowing what... the water presently is near perfect... I even added AC back into the filter a few days ago to clean the water a bit..also did a mid-week suck of some of the poop...but still... they can just die like one did this morning. (traumatic for a 5-year-old little girl...)

That 5 happened so close together does indicate something that affected them all. What is your water temp? What is your pH?

We have found that the guppies we got from one store were far 'stronger' and have lived, more than those from another store. It depends where they came from, and if they bring bugs with them.

And a mini-spike is possible when adding new fish to any tank - did you try keep them in quarantine? We've had to constantly monitor our with around 80 fry in it...

-G

Trott · May 10, 2018

Jenoli42 said:
i totally agree with your insights i hope we can help the OP because seeing dead fish when you look in your tank is a horrible feeling

Nothing worse than turning the tank light on in the morning and wondering if you lost another one..

ParrotCichlid said:
Just my opinion but i doubt this has anything to do with the filters or a mini cycle of any kind.

If the cycle had crashed to a level that would kill this many fish it would show on the water test. Parameters while not perfect are not the worst either. I find it hard to believe that 0.25 nitrite is enough to kill 5 fish on the same day.

I agree about 0.25 nitrite not being enough, dropsy affecting two older fish is curious though - that would have had to happen at least 5 days ago for the treatment to be complete (params may have been different?). Just a thought! Emfish, did you take a water test at the start of your Myaxin treatment?

ParrotCichlid · May 10, 2018

Trott said:
Nothing worse than turning the tank light on in the morning and wondering if you lost another one..

I agree about 0.25 nitrite not being enough, dropsy affecting two older fish is curious though - that would have had to happen at least 5 days ago for the treatment to be complete (params may have been different?). Just a thought! Emfish, did you take a water test at the start of your Myaxin treatment?

The main reason i think its nothing to do with the cycle is because the tank has no ammonia. With a mini cycle causing nitrite i would expect at least a little ammonia.

Of course i could be wrong though!

Jenoli42 · May 10, 2018

ParrotCichlid said:
The main reason i think its nothing to do with the cycle is because the tank has no ammonia. With a mini cycle causing nitrite i would expect at least a little ammonia.

Of course i could be wrong though!

That's why i asked if the OP had tested parameters daily since the filter swap. there may well have been an ammonia spike and if the OP wasn't testing, it could have been missed, followed by a nitrite spike they only caught at .25 once fish started dying, but the mini cycle was basically over by that point.

If the OP did all that though, then yes i do tend to think it's a disease brought in by new fish. i assumed they weren't quarantined by what the OP said, but if they were then i'm back to being stumped. *chin scratch emoji*

I guess we'll hafta see once the OP replies

Jenoli42 · May 11, 2018

emfish said:
Omg I have woke up this morning to all of these amazing replies. I will try to answer as many of you as possible...
I tested the water before the treatment and it was perfect
Ammonia- 0
Nitrite- 0
Nitrate- 30

I don’t usually quarantine the new fish... no..

I didn’t think it was a cycle. Could be the addition to new fish??

just one more question to rule out a mini cycle (this is because random nitrites are unusual without an ammonia spike as well): did you swap your filter before or after the treatment?

if your answer is before then I'm betting it was the new fish.

Brannor · May 11, 2018

For the last few weeks I have done 50% water changes. Only tonight I dropped it back to 25%, though I noted my pH might be up...so that might end up with another WC tomorrow... (our tap water is normally bang on neutral with nothing but whatever chlorine they add. (35ppm TDS that after carbon water filter is only down to 32ppm).

-G

DoubleDutch · May 11, 2018

What's happening with Harlequins the last days ????

5 Fish Dead In One Day

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