Dither fish

I have heard and read people talk regularly about dither fish and their use. However, it always stayed a somewhat vague concept for me as I hadn't 'used' or experienced the effect of dither fish myself.

So when I bought the red beckfordi pencilfish being told it was a great dither fish, I was like 'OK, let's see what it does'.

They went into a tank with pygmy cories and 2 betta imbellis. The imbellis had always been shy, lurking in the vegetation to see what I would do and only come out to eat when I would be at a safe distance. Now a few days later, the imbellis are out and about, in front of the glass and even looking at me in that curious way only bettas know how to.

The cpd's I put in with the guppy fry; in my 6 gallon rimless where there is no place to hide. For those that don't know: cpd's like to be in dimly lit tanks with lots of vegetation where they can hide and feel secure. Otherwise their colours will fade and they will stay at the bottom hardly moving.

Well, these fish are nicely coloured, come up to eat; even fight with the fry for food and swim happily up and down the tank.

It seems that I start to understand the concept of dither fish! The only experience missing is how these fish apparently can also promote spawning. Anybody that can give some examples and experiences on that?

The fish that hides is worried about predators. The shoaling dither depends on safety in numbers. But if the dither stays alive, the more cautious species will see some proof it's safe to come out and move around. If the small, vulnerable pencil fish isn't taking cover or releasing alarm chemicals, then maybe, just maybe, there are no predators around.
So the more cautious, bottom oriented fish ventures out. It is not attacked, and sees no danger. It registers the dither fish see no danger either, and it relaxes.
Dithers only help breeding in pair bonding fish. The pair can turn on each other in a small fishtank, but the dither poses a threat to their fry. And so, they will unite to confront the shoalers, and forget about problems with each other. This can get dithers killed, but it isn't common in a large enough tank. No dithers can get one of the partners killed.
We manipulate shoaling behavior to control (to a degree) territorial behavior. We use fear responses from fish that have an entire other set of reactions to danger (dithers) to calm nervous fish. It works.

So, could I use dithers potentially to ensure that my angel pair stops quarreling and gets down to business? I have added the juvenile angels in the hope that she will calm down and accept her male before he goes off with another but until now this hasn't worked.

I assume I have to take another species for a dither, but if there are not yet eggs or fry could this actually work?

I saw the proof that dithers worked when I bread Kribs. I had 6 rummynose tetras with them so instead of fighting with each other they seemed more concerned with making sure the somewhat oblivious tetras didn't come near the cradle.

Angels are hard on dithers, because they are skilled stalking hunters. They tend to get their targets more, unless the tank is huge. I bred mine with tsngles of hornwort and pencil fish, hatchets and rummy noses in a three foot, one meter tank.
When there are dithers and eggs or wrigglers, you have to leave a night light on. Cichlids defend visually.