How many friends do I need to get for my lonely Cory?

[AlphinaNovaStar]

I am thinking of getting some new friends for my lonely Cory some time this month. Well he is the only catfish in the 55 gallon aquarium. I have been meaning to get more fish but life issues got into the way. Once I can get to Petsmart with some funds I want to get some more cories as I think they are a schooling fish which means they might get lonely if it is just one of their species, right?
I know the new cories will be smaller than my Cory and might be a different breed. I know I can get him ided but I am not sure how easy it would be find the same type at petsmart. How many cories should I introduce at first? I also do not have a quarantine tank set up for two reasons, one I have no room for one and another is that it is being stored at my mum's place. Keeping that in mind and that I have a budget, what is a good number to introduce to Cory (yep that is his name and his species too)? I rather do several batches of catfish than mess up on only one.

 

[Jessie J.]

Yes, they will get stressed with only one and should have at least six other cory friends. Introduce two or three at a time if your tank is new.

 

[Colin_T]

Post a picture of your current catfish and we can identify it here. Set the camera's resolution to its lowest setting and use the flash.

As mentioned by Jesse J, Corydoras should be kept in groups of at least 6 and preferably more.

How long has the tank been set up for?
If the tank is less than 1 month old then don't add any new fish until it has cycled. If you don't have test kits, take a glass full of tank water to the local pet shop and get them to test the ammonia, nitrite, nitrate & pH for you. Write the results down (in numbers) when they do the tests.

Assuming the aquarium is established and has a functional biological filter, then just add 5 new catfish at the same time. Check all the fish in the shop tank before getting any. If any fish in that tank is not looking right, then don't get any fish from that tank. Look for fish that are rubbing on objects; have clamped fins; have grey, white or red patches, or any sort of weird film over them. If any fish show any of those symptoms, do not get anything from that tank.

 

[Byron]

Responding solely on the question of numbers...in a 55g tank and assuming the other fish are compatible and not crowding the space, you should aim for 12-15 cories, or even more. The more the better, always, with cories. [Now, this is ignoring the new tank/cycling issue.]

Second, when adding a shoaling species like cories, it is always better to add all of them at the same time, and not a few at a time. They will always settle in faster, and that means less risk of problems. Newly acquired fish are under immense stress and the more of them there are together, the quicker this will resolve.

You do not need to worry about different species, all cories will get along, and size of the individual fish is also not an issue. It is best to have a few of each species, but again the total number of cories is more important. I have some 12 species in my 70g, and there is only one or two of some of the species up to 8 or 9 of others, solely because of availability. They all chum around very happily.