Originally Posted by librarygirl
Do you know if they are males or females? If you have two males and one female that could be the two males trying to assert dominance and showing off for the female. I have them too but I have 8 (started with 12, 4 died along the way and planning to get a few more). I haven't noticed much aggression with mine, a couple of the males will square off now and then (they swim in a tight circle as you mentioned) but no attacking or injuries. I'd suggest increasing the numbers and try to get more females than males and it should calm down. They are more fun to watch when in a larger group too and it'll help them feel safer.
Thanks for the help. I am willing to increase the number I have, but here's what else I have in the tanks: #1 55 gallon - 5 angels, 2 turquoise rainbows, 2 blue and 1 gold gourami, bn pleco and now just 2 danios. #2 55 gallon - 4 angels, 2 opaline gourami, 4 rosy barbs, 2 bn plecos, and 1 danio. So is it even possible to increase that many danio in either of these tanks? I do really enjoy them and have already ordered 3 more. Any suggestions.