In my experience, giant danios can be nippy and they get large. They shouldn't be considered peaceful because of that, but they aren't as territorial as something like a cichlid or as predatory as a catfish or gar. So, they lie in the middle of an "aggressive" and a peaceful fish. I know a lot of people that recommend or use them as dither fish for cichlid tanks because they're quick, large, and not easily stressed.I was wondering if they are semi aggressive?