Mystery Of The Torn Fins

[CoryFever]

I have a five gallon quarantine tank with 3 aeneus cories in it. The only other resident is an ancistrus (aka bristlenose pleco). This morning all three fish were fine, but when I came home one cory had his caudal fin was shredded to pieces. The other two had their dorsal fins ripped. Who is the culprit? All four fish have lived in piece for the past week.

 

[Ninjouzata]

I'm not sure how inclined any of those would be to hurt the other tank mates..what sort of decorations do you have? Maybe some sharp wood?

 

[CoryFever]

I only have a smooth rock and some ludwigia repens

 

[Ninjouzata]

I have no idea then Hopefully someone with more experience comes along.
I do have both of the fish in question but have never seen them do anything to each other that could mess up their fins.

 

[Meeresstille]

Could their fins have gotten sucked into the filter intake tube? 

 

[star4]

It is a possibility, Fins can get torn quite easily, stress can also be a factor, if something has spooked them and they have rushed around the tank they can tear fins. Is it only the dorsal fin? check the other fins for any signs of tears, if they are ragged it could be fin rot starting.

 

[CoryFever]

I know it's not fin rot, but I am treating it as if it is. As of now, all three cories have ripped fins. The ancistrus is doing fine, know fins torn. The filter is very weak when it comes to intake.

 

[DoubleDutch]

I'd test for ammonia / nitrite. In a 5 gallon with an Ancistrus parmeters van get wrong in an eyeblink.