HI,
I have been doing some reasearch on corys and it says they should be kept in groups of 6 or more. I have 2 bronze corys that are full grown and I just bought two young panada corys. they don't seem to be hanging around each other. they just swim around in there pairs but never go into the same caves. Is this because of the size difference, or do corys prefer being with their on breeds. when they say keep in groups of 6 does that mean I need 6 bronze and 6 panada? I would really like add 2 peppered cory, and 2 albino corys and may be 2 skunk corys to the tank but I want them to be on big happy family.
Corys will happily mix if they look similar, eg sterbai with trilineatus, metae with pandas. If their markings are quite different then they may keep to their own kind much more.
This does break down a bit if there are enough fish. I have about 30 in one tank made up of seven species and you frequently see inter-species groups, though there are often single-species groups as well, all within a shoal.
I'm sure size is also important. They seem to group by both species and size while the size differences are marked but it breaks down quite quickly as the smaller ones grow.
I have 3 green corys and 1 spotted cory. The green corys seem to be with each other a lot and they leave the spotted one behind. My spotted cory dosent seem to be very active, so I should get some more of its kind. I think that if you have any corys that they should have at least 4 of their kind together.
The big danger with adding just two of each species is that you may end up with just males of one and females of another, and then there is a danger of crossbreeding, which is in my opinion not desirable. This is an area that tends to trigger strong debate and I do not want to go there here, but if you purchase pairs or multiples of then the crossbreeding problem is unlikely to occur.
From a behavioural aspect, I have kept several species together in groups of two to seven and found that even though they do tend to congregate in similar areas, those of the same species will usually be found together, often seperate from other types.
In a 4' x 2' tank a trio of C. trilineatus pretty much kept to themselves and hid in the shadows up the back, where the other corys rarely spent any time at all. Yet in the same tank C. concolor and C. adolfi were inseperable.
Personally I like to keep larger groups of one species rather than "a little bit of this and a little bit of that". It's a much prettier sight to observe a large school of similar Corys working their way around in the tank Try it and you will see
And I really think that the happiest Cory is a Cory living with lots of others of his own:-) (just my opinion) I never buy a new Cory species if there are fewer than 5 or 6 left in the shop. That's a minimum number.
Mixing species is absolutely fine. However, as already stated, make sure you keep at least 4 of each species, preferably 6+ as they are more comfortable in the company of their own species, but will mix well with other cory groups too.
Try it and you will see