Juli Cori Dead..dwarf Gourami And Banana Plant To Blame?

[chelsiethegreat]

i've had my 15 gallon tank cycling for over 2 years now.. 
 
i have now have only 3 cory cats. 2 emeralds, and one juli. And 1 dwarf gourami.  
 
i had two of each, but here recently, after purchasing a dwarf gourami and a banana plant the other day from a local fish store, my other juli passed. 
 
i haven't seen ANY aggression from the gourami to the cories..
 
the banana plant i bought seemed to not take to my tank environment at first, but now after some root growth, and a new stem and leaf, it seems to be okay.. though the coloration quite red..
 
 .... any ideas?
 

 

[Meeresstille]

Some plants are treated with chemicals, so it is always good to at least give them a good rinse before putting them in your tank. Also you may want to check if the plant that is labelled as banana plant truly is the aquatic banana plant, it can happen that non-aquatic plants end up being sold in the aquarium plant section of an LFS.
 
Sometimes plants can also introduce diseases to your tank, and it is actually a good idea to quarantine them first. During that time you could also see if there are any hitch-hikers like pond snails on that plant!
 
You've had the tank for 2 years, and the stocking may be causing too much stress on your fish, reducing their life span! Cories should be in a group of 6 of their own species!

 

[N0body Of The Goat]

You have put too many unsuitable fish in this 15g, which is not going to help matters, regardless of the cause here.
 
Emerald Brochis reach ~8cm SL (plus tail fin) and deserve at least a 120x30cm footprint tank and six of their own kind.
Corydoras julii (probably missold C. trilineatus) reach 5.5cm SL (plus tail fin) and deseve at least a 75x30cm footprint and six of their own kind.
Dwarf Gourami do get territorial and can be a menace in communities.