Thanks Icedcold! That sounds very much like my cories!

So it sounds like it won't really improve by doubling the size. They will always be half not schooling -- probably an evolutionary trait that allows the whole community to be alert 24/7 perhaps.

I have a 20 gallon long tank with 5 Julii corydoras. They are very healthy and happy, with good appetite and long barbs, often swimming in groups of 2-4 being playful and always scavenging. However, I rarely see them move together as a shoal in group of 5. Mainly I guess because they are on ...