What happened to my tank

[Peteostler43614]

So, I just lost 14 platys in two days. It started with all the fish swimming right at the surface of the water, then all of a sudden they started dying! When they were hanging at the surface I did a level check with my API master test kit and they were:
Ammonia 0
Nitrite 0
Nitrate 40.
Ph 7.4
Clear water
So..... I did a 30% water change to get the nitrate out. I used API stress coat and API stress zyme and API aquarium salt in the new water that was the same 76 degrees that my tank lives at.
The next thing I know one by one about an hour apart they all died. Nitrate dropped to 30 and ammonia and nitrite were still zero.
I looked carefully at the dead fish and there is no fuzz, white flecks, redness, scales sticking out, or anything wierd.
I feed them 3 tetra tropical crisps per fish twice a day, and everything was hunky dory until all of a sudden they started acting funny and dying.
The only fish that survived was a baby green Cory catfish.
I have 3 bubblers, 2 live plants, and a waterfall filter, so oxygen should not be a problem.
WHAT HAPPENED TO MY TANK?

 

[Shane87]

Only thing I can think of is it somehow got contaminated?

 

[Peteostler43614]

Will this transfer to any future fish I get? How can I prevent future fish from dying from this? How long should I wait?

 

[Shane87]

Depends on what caused it :/ if you still have a corydora alive then it can't be completely hopeless, do you know how it could have happened?? That's the best way to know how to deal with it and prevent it in the future, if you don't know then I would say clean every thing as thoroughly as you can and change any filter wool you have and add active carbon ( this removes most toxins ) but leave in the sponges and bio media and see how you go with the surviving cory for a week minimum, then I would add another 1-3 "hardy" fish like Platy, danios, harlequin rasboras, something like that and if they are of for a week or so just slowly add fish and you should be ok. Another thought I just had is was there a ph swing? Hope this helps, let me know if you need any more help and I'll try my best

 

[Shane87]

P.s. I would do as big of a water change as you can, maybe even 90%

 

[Candiceg]

To me it sounds like you could have overfed them. If they eat too much they can get bloated and die. This happened to me before when some of my fish ate a bunch of mollie babies and died same day

 

[Shane87]

Wow... I have never experienced that lol do they really just eat until they die?

 

[FlyAnglerFishKeeper]

I'm not sure about that, but I realized on week 1 with my platys that they are alot like a Beagle. They will eat as much as I will feed them.

 

[Shane87]

That's amazing if its true lol I have heard of them eating food that is to big and choking sometimes to death but never eating so much they die...

 

[TaylorAnuar]

Do you have sand substrate by any chance? I've hear of this happening if you accidentally disturb the sand too much at once (move a decoration that's been in place for awhile, planting a new plant, etc.) and release a bunch of that sulfide gas that can build up. Just a thought.

 

[Shane87]

I have heard of this aswell but wouldn't it show up on the test?

 

[TaylorAnuar]

If there's a hydrogen sulphide test (not being sarcastic) then yeah. Haha

 

[Shane87]

Interesting, I would of thought it would have affected the water perimeters and shown up on the API test somehow. Learn something new everyday

 

[TaylorAnuar]

Yeah, but it's really uncommon. I've only heard of someone losing there fish from it once, unless of course that's what happened to these fish.

 

[Peteostler43614]

To me it sounds like you could have overfed them. If they eat too much they can get bloated and die. This happened to me before when some of my fish ate a bunch of mollie babies and died same day

I am super careful to not oversees them. They eat and finish the food in about 1 minute, and the food says as much as they will eat in 5 min.....

 

[Peteostler43614]

I have gravel substrate in the bottom, and I had not vacuumed the gravel in almost a week. I do have a gravel bottom filter that I had not mentioned before

 

[Shane87]

If you have gravel and your levels are fine then I'm back to contamination, any idea if that could of happened?

 

[TaylorAnuar]

The only thing about contamination is that corys are super sensitive to contamination since they don't have scales. So i wonder if there's something that only applies to livebearers or something.

 

[Shane87]

What about if it is something that's more top level? Like oil based or something? Do you think that would make a difference? If its not contamination then I'm out if ideas :/

 

[TaylorAnuar]

I think someone more experienced needs to chime in. Hahah