Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
No matter how many fish you have of one species, there will always be one or two that will not hang out with the others. or wants to explore on their own. However, if you get more of the same, then the effect is much better, you will really see good schooling action. When there are too-few of a species you do not see the real schooling behavior, even if you are not missing one or two that are doing their own thing.
Look at it this way:
If you have 6, and 1-2 are off on their own, then you are looking at a 'school' of only 4-5 fish. Not impressive.
But if you have a dozen, and 3 go off and hang out by themselves, you still have 9 in the main group, and that looks like something. If the tank is large enough I would get even more.
Is the tank a tall style?
Or a standard 29 gallon?
Either of these has enough top space and floor space to mix the tank with half a dozen Cories, or some Hatchets (covered top is a must).
If it is a shallow, long or breeder style, then I would get more Rummies, maybe a few Otos if needed, but nothing else.