Corydoras and schools: different types make-up a school?

[Knew tooth is]

I've read that corydoras are schooling fish. With respect to the corydoras, could the school be composed of different varieties? For example, will bronze corydoras school with albino corydoras, or julii corydoras or any/all of the other types? Or, is a "school" strictly composed of one variety? Also, what would be the general minimum number of corydoras that would be considered a proper school?  

[JettsPapa]

Hello,

No, different species of corydoras generally don't shoal together.  The only exception is the albino varieties, since they belong to one of the other species (bronze I think), so they'll shoal with other fish of the same species.

Similar to how black skirt tetras, white skirt tetras, and glow tetras are all just different color variations of the same species and will shoal together, but that isn't true for other tetra species.

[Knew tooth is]

JettsPapa- thanks. Interesting about the albino schooling (shoaling) with another species.  I'll look further to see from which species the albino were derived. Anybody have an idea about the identification of this species? Also, what would be considered the minimal school/shoal? By the way, are shoal and school interchangeable terminologies? 

[Colu]

Corydoras  paleatus  and bronze cory  booth have albino forms

[Knew tooth is]

Dear Colu- makes this more complicated, and even more interesting!

[CorydorasEthan]

In the wild, Corydoras can be found in groups of hundreds or even thousands. With this information, one can presume that all Corydoras need to be in groups of their own kind - preferably six or more of a single type - to school or shoal nicely and to interact and behave naturally with one another.

One exception to the rule of six or more is albinos and bronze/greens, because they are the same species (unless you have albino paleatus so put those with peppers). This allows you to mix several albinos with several bronzes to meet the same interaction and social needs of the cory. The only downside to this is that the albinos might not be able to breed with the bronzes (at least in my case). I have several albino females and a male bronze cory (all aeneus). They spawn frequently, but the eggs are never fertile. Other people may have other experiences so I would check with them as well.

I, however, despite doing a lot of research on keeping Corydoras, still can't seem to abide by the own rules I suggest others to follow. In my 29 gallon currently, I have 2 adult paleatus corys, 4 baby paleatus corys (their offspring), 1 bronze cory, 2 albino corys, and 5 pygmy corys. Because this is the only tank I am allowed to keep (with the exception of my 10 gallon breeding tank that I am about to set up), I wanted to have as many types of corys as possible, as they are my favorite fish. These fish (besides the babies and pygmies) are all fish I found were alone in their LFS tanks, with no other corys at all. This "lonely cory" situation, as I call it, is mostly why I keep multiple types of corys in less-than-ideal group sizes, as I wanted them to have a more social life with more corys to interact with, even if they are varied species. As a solution to this problem, I found breeding my corys that are the same species helps to increase the school size. In terms of behavior, all my corys do fine, but only the albinos and bronze seem to be quite active. Everyone else seems to rest/hide during the day, and only come out actively during feeding time and during the night. I have seen my group of five pygmy corys schooling or shoaling around together tightly near the front of my aquarium occasionally, but they are very shy otherwise.

To summarize, try to keep several of one species of Corydoras and they will do just fine. If you wanted them to properly school together and exibit natural behavior, I would get around 6 or more.

Thanks for taking the time to read this. I hope it helps.

Edited December 28, 2020 by CorydorasEthan