All the fish have different advantages in an aquarium of predators. The danios have speed on their side above the BA tetras or the silver dollars. But if physical contact is made, I would list them as the least likely to survive. Tetras are in the middle. They are good schoolers and there is safety in numbers. If one strays from the group, the cichlids may make a go for a snack, but the BA tetras are also pretty fast and should be able to escape pretty easily (just like a danio would). The silver dollars are shoalers. They don't really school. However, their advantage is their great depth. None of those cichlids is going to think "I can fit that in my mouth". They can also take a pretty good beating. I would list them as most likely to survive any physical contact that is predatory. If you have a mean fish though, forget it. The dollars are the easiest to catch and even though they can take a beating, a fish that doesn't want to eat it and only to destroy it will be able to do so.
If you want a schooler, give the BA tetras a try. Worse case scenario is you have to rehome them and try something else. They are cheap dithers for a 3" fish, so there won't be much financial setback if you have to do something else.
If the tetras fail for any reason, the choice between danios and dollars comes down to the aggressive nature of the individual fish you have. I doubt you have any nasty fish since a 120 with four ultimately 10-12" cichlids is pretty maxed out. So if you don't have a nasty fish, the dollars will work just as well as the danios. If aggression is an issue, the danios will do the best.
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