one cory is different species than the rest, stays by itself mostly. advice?

[ptero]

I have five corydoras sodalis in my 20g, or so I thought. one of them is in fact a corydoras reticulatus. I didn't notice until today that it had the black spot on it's fin. I've also noticed it's pretty much a loner, and generally doesn't school with the other corys.
I'm afraid that their ostracizing it and it's feeling stressed. It swims around the tank by itself, or just sits in their hiding place while the others scavenge around.
I'm thinking of getting more reticulatis to make it feel more comfortable. what is ya'lls opinion on this?
I currently have 5 corys and 8 black neon tetras in a moderately planted tank. any advice would help greatly.

[fishmommie]

corys are generally happier in schools of their own kind, as you've figured out. You could return the single and replace it with one like the other 5 or you could add five more of the single and 1 of the reticulatus. If you're a big fan of corys, this works great because you'd be pretty well stocked at that point.

[talldutchie]

1o medium to large sized cories in a tank that size is a very well stocked tank.

[SueD]

I think it also makes a difference if this is a 20 long or 20 high. I don't think I would put 10 cories of that size in a 20 high. I'd return the odd man out and replace him with one of the others.

[Knightia]

+1 to that

Return the loner to be with its own kind and get another for your current group.

[DoubleDutch]

Agree with that !!!

[Byron]

I have had success (over 25 years) with corys kept in groups of several species, with some species as a lone fish and others with 2, 3, or 4. I usually try to get five of a species, but this isn't always possible for various reasons.

In your situation, I would tend to either get more of the loner, or return it...but I would only do the latter if the store has more of this species. I am not going to send a lone fish back to the store where it will be even more stressed than in my tank, not to mention the considerable stress of yet another move for the fish. Corys do not appreciate changing environments, and this is why many don't make it.

If you do get more, I agree you only have a 20g but this should not be an issue if you are regular with your weekly water changes. And having plants helps a lot, even just floating. Also, lots of chunks of wood for the corys to find a home. I have some species...and C. reticulatus is one of them...that I never see except during feeding time, and I have six of this species. These spend their entire day under cover. They are out and about in pitch darkness though; fortunately I can enjoy them when they are feeding.

Byron.

[ptero]

thanks for all the advice you guys. Unfortunately, the aquarium store where they came from no longer has the same species for sale. Mine were actually the last they had, and they were all wrongly marked as C. Reticulatus (except for the one). I'm just gonna keep an eye on it and hopefully it'll eventually integrate with the others.