That's perfectly fine. I did the same thing until one got to be 4 inches long and killed everything else in the tank.i cycled my tank with danios that's why i'm building a stocklist around them cause i think i have gotten a bit attached to them. lol
I'm not saying this is going to happen to you, but I have learned I don't personally like them that much.
Make sure the match the activity level of the danios with that of any fish you plan on having in the tank.