Yes! That is it! Thanks! Interesting to hear about their schooling behavior. Looks like mine are full grown or on the large size….Glad to know they don’t become aggressive usually.
I don’t really understand about the schooling….I only have 2 (don’t want 6 of them anyway)….if they aren’t aggressive now - does the lack of a school make them more stressed / aggressive?
They did eat one of my large snails…
As I already tried to explain, shoaling fish like cyprinids must have a decent-sized group. This means close to 10 or more. This need is in the genetic code of the species. The fish expects to be in a group for safety, normal hierarchy, etc. Scientific studies have proven that fewer than 10 means increased aggression. Now we need to look at what "aggression" is here.
Naturally aggressive species become considerably more aggressive. I don't think we know why physiologically, we just know that it happens most of the time. More rarely the opposite can occur, the lone fish literally pine away, weakening and succumbing to various problems they would/should normally bee able to easily handle. Species that would normally be what we would certainly call peaceful will become aggressive. There are many stages to aggressive, but the fish in too small a shoal will exhibit aggression.
There is also a latency to feed from being in too small a shoal. This may not seem like a problem, but the fact is that it is extremely enlightening--a fish that is reluctant to feed is certainly under a considerable level of stress.
To be blunt about this...to deny a shoaling fish the number of its own that it expects is inhumane. If you cannot provide what the fish must have to be healthy and normal, you should not have that fish. This is why research is so crucial. Another member,
@GaryE , posted a thread today on the subject of bullying, and it contains a lot of bang-on good sense information. All aquarists have to learn this if they want to be successful and have a tank or tanks of well adjusted, healthy and "happy" fish.
