Sudden mass killings in the filter?!

[millyp]

Was hoping for some help/advice:

Tank details: approx 11 gallons, ammonia 0ppm, nitrites 0ppm, nitrates 10-20ppm, has been running for a year now

I had 3 male guppies and 1 female (inherited her from a friend), so was worried about the m:f ratio and added 3 females about 2 weeks ago, along with a bottle of tetra safestart to be on the safe side. Then added another 4 females and 2 males about 5 days ago (I know, a lot- I had a moral crisis in the fish shop and panic bought).

There are four plants growing, logs and a couple of hidey holes. I realise it was overstocked, but I am due to get a 40 gallon tank from my brother soon so thought I could safely rescue a few from the grips of the nasty fish man...

Anyway this morning I checked and could only see 7 fish out of the 13. Found one dead on the floor, one dead in the filter outflow, and after much hunting, 3 more dead in a 'channel' that allows for the filter wire in the back. I have an open topped internal filter, so it's possible the one inside jumped in (can't have got sucked in as the inlet is covered in nylon), but I suspect he was also caught in the channel and washed up and over. No idea about the one on the floor but it's also possible he befell the same fate.

Have checked the water again (API master test kit)- all fine- and I'm absolutely baffled as to how it could have happened to so many fish so suddenly. They were ALL males as well, no females- could that be relevant?

Please help- I feel awful for the poor little things!

 

[millyp]

I've just checked on them again and found a female upside down, completely dead on the bottom. Only 3 hours ago they were all happily swimming around and ate when I fed them. Have re-checked the water and it's still all zeros except nitrates between 5 and 20ppm.

I'm totally stumped. It seems maybe it's not the filter's fault- but what could be killing them all so suddenly? Poison? Disease? They all look absolutely fine

 

[Fresh2o]

Wow! It's hard to say since they don't show any obvious signs of disease and the water parameters are normal.
Is it possible that something was introduced with the recent batch of fish? But the sudden death might indicate the presence of a toxin near the tank.
Do you recall if any aerosol air fresheners or cleaning products were used around the tank before the onset of death?

 

[millyp]

Definitely no cleaning products or sprays, they're banned in that room (and my partner never cleans anyway! I will double check that he's not sprayed deodorant or something in there but I don't think so)

I did wonder whether it could be the new bottle of stress zyme I've started using- I really am clutching at straws here- as I may have been overdosing, but I don't think by that much really...

 

[Fresh2o]

I would not think that Stress-Zyme would have such a catastrophic effect.
When in doubt, do a water change. Even though the parameters are fine, if there is something in the water, a partial water change should help dilute it.

 

[coralbandit]

+1 with Fresh.
If you are testing correctly(are you shaking nitrate part 2 like your life depends on it?)
Then it sounds like something is in your water.
Try water change and IMO this is what carbon is for...it can remove many things that we can't test for...
Good luck sorry about your gups.

 

[millyp]

Definitely testing correctly- I'll get some carbon today and hopefully won't have any more casualties. I feel so bad for the poor little things!

 

[millyp]

I've only been changing about 10% of the water each time I've found a dead one- do you think I should try a bigger change? Will go for 30% today and see if it helps.

 

[Fresh2o]

Yes, larger water changes. 30-50%.
What water conditioner are you using?

 

[millyp]

Sorry, I meant stress coat, not stress zyme, which is the water conditioner

 

[Toad]

That small a tank and that many fish, they may be harassing each other pretty hard, and if some of them were already in poor condition that would know them off. I had six males in a ten gallon and five of them chased the one till he died, then four started chasing one till he died.... you may need to get that 40 set up asap.

Sent from my SM-G930T using Aquarium Advice mobile app

 

[Autumnsky]

Agree with the pwc 30%-50% yes.

Do you know if your water supplier uses Chloramines? They are stronger- stay effective, and last longer than Chlorine and you need to know that the StressCoat is effective for Chloramines too (some water conditioners /dechlor. don't work on chloramines). Not sure personally.

Also the question of heavy metals which you can check with your water provider as well. Not all products neutralize/bind those too. Also the issues not you but if others read that you accidentally think the product you use is a dechlorinator, like Stresszyme which isn't (easy to confuse due the the similarity of name and it says BB will help treat ammonia, NitrIte and NitrAte sounds like it would.)

Otherwise possible illness, crowding stress. Jumping out usually has to do with a stress either poor water quality or tankmates (chasing).

If you clean your filter pads with tap water untreated, or replaced one with a new one before or around that time, you could have had a mini cycle with poor water quality.

So sorry for your losses. Hoping we can help with finding a cause.

 

[Swampman]

I too had a problem one the summer. Even with the AC on my tanks temp went to 82f. I lost a 10gal with babies. Every fish in the tank died over night. My other tanks temp were 82 -83f. The fish where all up on top. I lost a few but added an air stone to all my tanks. Even when the temp of the water was 82f the fish where fine. Warm water less oxygen in the water.