Random fish dying and not sure if i have an aggressive fish

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Jose Sanchez

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Hi
This is my situation I have a 72g planted tank, with
15 corydoras
17 neon Tetras
2 guppies
7 cherry shrimp
and a molly which was given to me, don't have any other tank to put him, but I have 5 months with him

So in the last couple of months, I had lost 3 neons (2 last month, one today) and I'm not sure what it can be, I have checked the water, for disease, etc etc.
a baby corydoras a couple of weeks ago
a cherry shrimp today in the morning

my parameters are good I check regularly with API test kit, besides the PH which I know is a little high for neon tetras (7.8), I do my water changes regularly every week, so I'm suspecting on the Molly, it has a history of being aggressive before but it seemed to be calm after I separated it for a while in a breeder box

Please if you guys have any idea :(,

I'm attaching a picture of my tank

Thanks in advance for your help! regards from Mexico
 

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Can you give us any details about the fish that died? Any symptoms? Did they look or behave abnormal in any way?
 
Can you give us any details about the fish that died? Any symptoms? Did they look or behave abnormal in any way?
yes the fish was behaving normally, just some chasing between the neon tetras every now and then (this could be also an issue?), the corydora just was very still from one day to another and that same afternoon died I inspected it but no visible injuries and the cherry shrimp just was dead in the morning.
I keep track of my water parameters
PH 7.6 - 7.8
Ammonia 0.0
Nitrite 0.0
Nitrate 5 ppm

Thanks for the reply
 
I'm afraid this is a bit of a mystery.
Male neons will chase each other to establish a hierarchy but it usually settles down.
The cory being still is not that unusual, especially if it is an old fish.
I had mollies years ago but I don't remember them being aggressive. Maybe try separating it again to see if it makes any difference?
If you are not too familiar with fish diseases you could read up on it and observe them to see if they display any symptoms. If you're unsure post on here to get advise/ opinions.
Sorry I couldn't be much help.
Good luck with your fish.
 
I'm afraid this is a bit of a mystery.
Male neons will chase each other to establish a hierarchy but it usually settles down.
The cory being still is not that unusual, especially if it is an old fish.
I had mollies years ago but I don't remember them being aggressive. Maybe try separating it again to see if it makes any difference?
If you are not too familiar with fish diseases you could read up on it and observe them to see if they display any symptoms. If you're unsure post on here to get advise/ opinions.
Sorry I couldn't be much help.
Good luck with your fish.
Appreciated, i have some experience with the usual desases (ich, bloat, etc) the corydora was still but not as the other, sorry if i don't explain myself clearly im not a native English speaker, it was being dragged by the flow.
As far as I know, guppies neons and Cory's are not aggressive so the moly is my odd guess.
Ill try to separate it again

Thanks
 
Your tank is beautiful, I'm sorry you've been having a rough go of it. I've never heard of a molly killing other fish. Males chasing a female too much, yes, maybe even to the point of exhaustion and thereby killing her. Eating shrimp? Sure. But attacking and killing cories and tetra? Very very unlikely...

Some fish will pick on a fish that is ill and weak though. Have seen both guppies and platies do this, so perhaps the aggression you were seeing was this sort of behaviour? Some territorial chasing is also normal especially for male mollies, but they certainly don't usually take it to extremes or go after fish like cories.

I'm sorry that that's such an unhelpful answer. Just a few more questions?

What temp is the tank at and is it prone to temperature fluctuations?
How long had you had the neons? Neons are known for being pretty weak now as a result of poor mass breeding.
How long had you had the baby cory and what species? Panda cories especially are also known for health problems thanks to mass breeding due to their popularity.
 
yes the fish was behaving normally, just some chasing between the neon tetras every now and then (this could be also an issue?), the corydora just was very still from one day to another and that same afternoon died I inspected it but no visible injuries and the cherry shrimp just was dead in the morning.
I keep track of my water parameters
PH 7.6 - 7.8
Ammonia 0.0
Nitrite 0.0
Nitrate 5 ppm

Thanks for the reply
Everything sounds just right with your water perimeters, is you molly a male as they can be aggressive towards other fish, i had 5 in my 60 gallon tank and all the same fish as yourself except the shrimp and the mollies was all male, they was chasing at one another, then turning on my other fish.
I soon removed them and took them to our local pet store and as soon as they was removed peace came back.
 
One other thought, just in case it's not a rogue molly.

If your GH is high the soft water fish (neon and cory) will struggle and be prone to disease. Do you know the GH?
 
One other thought, just in case it's not a rogue molly.

If your GH is high the soft water fish (neon and cory) will struggle and be prone to disease. Do you know the GH?
Well i don't know the GH for my water just the ph 7.6 and we have hard water here and mine cope fine, even though it's higher than it should be but apparently they can cope well with hard water.
 
Well i don't know the GH for my water just the ph 7.6 and we have hard water here and mine cope fine, even though it's higher than it should be but apparently they can cope well with hard water.
The question is for the OP.
 
Hola! Si quiere puedo ayudarle traducir lo que quiere decir.
Edit: Am I allowed to do this? I basically asked if OP feels more comfortable speaking spanish I can help translate.
Gracias! Puedo leer inglés sin problema, solo aveces batalló para darme a explicar
 
Your tank is beautiful, I'm sorry you've been having a rough go of it. I've never heard of a molly killing other fish. Males chasing a female too much, yes, maybe even to the point of exhaustion and thereby killing her. Eating shrimp? Sure. But attacking and killing cories and tetra? Very very unlikely...

Some fish will pick on a fish that is ill and weak though. Have seen both guppies and platies do this, so perhaps the aggression you were seeing was this sort of behaviour? Some territorial chasing is also normal especially for male mollies, but they certainly don't usually take it to extremes or go after fish like cories.

I'm sorry that that's such an unhelpful answer. Just a few more questions?

What temp is the tank at and is it prone to temperature fluctuations?
How long had you had the neons? Neons are known for being pretty weak now as a result of poor mass breeding.
How long had you had the baby cory and what species? Panda cories especially are also known for health problems thanks to mass breeding due to their popularity.
The baby cory was born in the tank in March, is a paleatus or peppered, the tank is at 77,78 F constantly
The neons are just a couple of months since I bought them
Thanks!
 

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