Question about schooling fish

Schooling is a group reaction to threats. Many small fish in a group have a better chance of surviving a predator's attack than the same number of small fish spread out. Similar to animals that herd together. General behavior: all the fish are in the same general area (within 1-2 body lengths from each other) and move together. Not synchronized (like a flock of birds), but generally staying together over time.

Neons are quick learners--if there isn't anything they see as being a threat, they won't school. Usually a bigger fish is enough--for example, my rainbow shark cruising around brings all my tetras into a nice school. When it's hiding in it's cave, they spread out. Rainbow chases the neons a bit, but hasn't done more than that.

In a small tank without something like a paradise fish, they won't school for very long. 5-6 would be happier than the current 2, but you'll need to really watch your water conditions too make sure it doesn't become unstable. As long as the new stock is healthy (advocating a quarantine tank), they'll mix with your current pair just fine.

That's exactly what schooling means, and they're beautiful when they do it. It's no secret that Cardinals are my favorite fish, and Neons are quite similar in nature.
You could add a Black Angel to that tank and with good filtration it should be fine. And the Angel will, for the most part keep them schooling nicely. Especially after he matures some.
Len

An angel will get way too big for your 6 gallon tank. A paradise fish would be a better choice.

Agree w/djlen on the meaning and occurance of schooling, but you just are not going to see much of that in a small tank. For schools to form and move in a synchronized manner, space is absolutely required. The threat does not have to be real - apparent threat works just as well - long tanks, ends/back corners heavily planted, center open or carpeted, schools form and coordinate crossing the "plain" with no "threat" species present - the open space is in and of itself a threat.

But here OG's advice is appropriate - the tank is too small for zones to be established and nearly too small for a school to establish - little or no chance of coordinated movement beyond a brief straight line.

All IME & YMMV

But it a wonderful justification for buying 6' tanks - "but Dear, we won't be able to set zones without at least 6 ft." - and that works so well, you justify another, and another...

I have been told by my LFS that a school of tetras less than 10 fish is under stress.
And we want to avoid stress.

This was particularly evinent when one of the Cardinals
fell into the tank next door. You could see the poor sucker
was a typical stress puppy.

The minimum school I try to keep is 10 but I try for 12 minimum when I can.

An observation. Tetra Cardinals loose color at night
when they 'sleep'. They also spread all over the tank
with each fish finding a 'bed' for the night.
It freaked me out the first time I saw this.
I thought there was some chemical imbalance in my tank
all the Cardinals lost their color.

When a cardinal is sickly the bright fluourescent
stripe will pale. Its a good sign that something is wrong.

More is always better with schools, but none of us know what minimum adequate unstressful school size might be.

I would not have a smaller school of Cardinals than a dozen. If I had my druthers I'd have a thousand and the appropriate tank to house them.
Len

why don't you get some rummy nose tetras instead, i hear they school better than neons...