Cory type?

[Iris94]

I got 4 cories from petsmart, all were called emerald cories. I've had them for about a month now and 1 has grown much bigger than the others and is also much darker. Does anyone know what type that cory really is and how big it will get? Thanks!

Sorry about the blurry pic, I'm using my phone.

 

[Sharpchick]

Emerald cories have had their scientific name changed a gazillion times. Mostly it has to do with the fact that they have more than 10 rays in their dorsal fin, where members of the corydoras sp. have only 7. Scientifically, emerald cories are brochis splendens. They are also true bottom dwellers, usually only racing to the top of the water to gulp air occasionally.

They can get to about 3 inches, and are some of the larger armored bottom dwelling cats. Unless you keep them in numbers of about 5 or more, they are usually very shy.

That's what you have in your photo.

 

[Iris94]

Ok. Do you know why one of them looks so different from the others?

 

[absolutangel04]

I will also add that females generally get a fair amount bigger and rounder. Some color variation is normal, nothing to be concerned about. The size indicates that your large dark one is likely a girl. There is a chance that she is one of the rarer, but similar looking species who happened to slip into the group, but my guess is that she just happens to be a bit darker.
I disagree about them being shy unless you have 5. They will swim around together, but cories are not tight schoolers and do fine with just a couple. 4 is fine.