Random cory deaths?

[xDestro]

Over the past 2 weeks iv lost 3 juli corys, my water perameters are perfectly fine, keeping up with water changes, all other fish are doing great so any ideas? Maybe it's time to clean my filter? Maybe they get scrapes from my gravel? ( ik I should have sand with corys newbie mistake) ik fish deaths are kinda random here and there but this seems unusual

 

[deeda]

What are the water parameter results?

Are these new fish or have you had them for a few months?

Did you see any damage to the fish such as worn off barbels, nipped or damaged fins, etc?

 

[Warborg]

Cories are a tight knit group. I've seen it first hand where several will die off back to back. In fact I think I just lost 4 in the last 6 months.

 

[Lepisosteus]

What's the temperature? Where did you buy them? Did they look healthy?

 

[xDestro]

0 ammonia 0 nitrites roughly 20 nitrate

Temp at 78-79.

Tanks been running for a little over 6 months.
Corys have been in there for probly 5 of those months.

Bought 5 of then from a family owned store.

I didn't see any damage to then when I took them out and they looked healthy. I did notice the past 2 months they were less active, just kinda laying around here and there.

 

[duanes]

What species of cory are they. Depending on species, and where they come from in South America determines water temps and perameters, s ome prefer warm water if they are from northern S America, some species if from southern South America prefer cooler water.
And those differences can be important in keeping them healthy, S American isa very large continent with many different temperature zones.
I kept Uruguayan C. erhardti in unheated tanks of about 68'F, warmer temps made themproneto disease and fungal infections.

 

[Skalper666]

I got this one.

Fight Club.

 

[xDestro]

Juli corys