Sudden fish die-off

[jmh59]

Hi;

Newbie fish keeper here with a bit of a problem with my tank. Its a 20
gal that has been running for nearly 5 months. Until last week, it has
been inhabited by an adult dalmatian molly, 2 of its offspring, and an
adult platy. The tank seemed fine, as the molly managed to have 2
small batches of young, 1 of each that survived. I typically do a
10-20% water change weekly, with algae scraping. Last week, I added 4
head-and-taillight tetras and 3 runny nose tetras. All was fine until
the next week, when all of the new fish died within a 24 hr period. I
did a 10% change on saturday, and they were all dead by Monday
afternoon. The mollies and platy were apparently unaffected,
suggesting that I didn't spaz and forget to treat the water. I checked
the water Monday night. The pH was a little high at 7.6, and the
nitrates were 0.5 ppm, but ammonia and nitrites were 0. I did another 20%
change Monday night. On tuesday AM, the adult mollie was looking listless and hiding. The platy was hiding too, but that is not abnormal for him. The offspring still look fine. Thinking that there is a toxin, I replaced the charcoal (but not the sponge) in the filter.

Anyone heard of this before, or have any insights? I'd hate to lose the last ones too.

Thanks in advance

John

 

[Bloo]

Oh dear I can only think that you added too many new fish as you more than trippled your filter load in one go. This probably cause a spike
That's my guess anyway.....

 

[WILDER]

Were the fish gasping at the surface, some thing could of got in the tank like a house hold chemical, no chemicals in the bucket of water you added to the tank, or the new fish fetched something awful into the tank.

 

[jmh59]

Thanks for the reply.

No, I use only dedicated buckets etc to handle the water. The fish seemed to go quietly. For example, the head and tail light tetras hung suspended near the surface, but wouldn't eat or chase each other. Wasn't a violent poisoning kind of thing.

I'm looking into the water company to see if they changed chemicals. Apparently chloramine is more difficult to remove with the dechlorinators? Also a little concerned about the elevated pH.

John

 

[WILDER]

Keep an eye on water stats, sure it didn't go into a little mini cycle with adding the new fish, just a possilbility.

 

[3fsh]

Definitely too many fish added at one time. With the few fish you had in there, the bacteria couldn't cope with the sudden overload. I'm sure it cycled quickly, though, because you didn't get any ammonia readings.

How long did you acclimate the new fish? The standard is to float the bag for (at least) 10min and then add a little bit of water every 5min for a half an hour. Then dump out half of the bag's water and repeat the process for another half an hour. Then, and only then, you can release the fish into the tank. I prefer the drip method myself... but this method works just as well. Sorry for your losses.

 

[jmh59]

Thanks for your replys. I think I have the situation figured out. When I tested the water, as I mentioned, the pH was a little high (7.6). Turns out the tap water is now 7.6! Never had this problem - I am attempting to call the water company to find out if this is new. Anyway, I think the high pH especially stressed the tetras. Also, since I posted, the molly and the platy died of what looks like ick. So one possible scenario is the new fish came with ick, which wouldn't have been an issue if everyone wasn't stressed by the higher pH. The tetras, being more sensitive, died fists, whereas the mollie and playty needed the extra time to build up a fatal ick load. So it looks like an unfortunate water change incident and naivete about ick on my part.

I have now added salt and Coppersafe to the water in an attempt to kill the ick and save the 2 baby mollies that are left. Anything else I can do? My understanding is the parasites on the fish are not vulnerable to medication, only the infective swimming stage. I used coppersafe because I wanted to avoid the staining and potential killing of the biofilter by the malachite green/formalin products (ie. quick cure and maricide). Also, should I add antibiotics as well? And finally, I have read that salt alone is usually enough to kill the ick. Any truth to that?

Thanks

John

 

[sylvia]

Do lots of water changes. If you had an ammonia/nitrIte spike (do you have a test kit) - which is what I think happened judging by your description of the fish hanging at the surface - doing lots of water changes will be a big help (though the tank should have by now stablized). Treat the ich with an anti-ich med but don't add anything else to the water. Antibiotics etc should only be used when absolutely necessary and prefferably in a hospital/isolation (seperate) tank as they kill of the good bacteria in your tank and can cause ammonia/nitrIte spikes in this way. I seriously doubt, BTW, that the ich killed your fish so quickly - it can take a very long time for ich to kill even small fish. If you didn't acclimate the new fish properly, however, there is a chance that the sudden shock from the change in pH from the LFS to your own tank could kill them. Only the new fish would be affected by this obviously.

 

[sylvia]

Oh just wanted to add - they aren't ruNNynose tetras! They are ruMMynose tetras.

 

[WILDER]

Sorry for your losses, R.I.P.

 

[Bloo]

John, a PH is 7.6 is absolutely fine for most fish and certainly the fish you have there, so I can't see that being a problem at all.
As for the ich, I really would only use anti-ich meds. It's really not expensive and works by far the best in my opinion. And you can most certianly get ich meds that will not in any way harm your bio filter - just check with the lfs.
Good luck.