danios and guppies

I have 4 active zebra danios that like to chase each other.  I am getting a pair of guppies soon but I am worried that the danios will nip the guppies fins.  Will they or not?
Also I have noticed that one or two of the danios have slightly torn fins probably from an aggressive one.  I really want guppies but if the danios are going to tear them up then I guess I cant.
If it matters, I have a 10 gal with the danios and 2 female platys.  My nitrites are less than 20 ppm.  Nitrates are less than 5 ppm. My temp is normally at 76-77 F. My ph is about 8

 

Emma,
It sounds like you tank isn't completely cycled if you have nitrites, or you are having a minI cycle. I would not add any more fish to that tank, even when your nitrites get back to zero. You pretty much have a full load in that tank. You might be able to add 3 pygmy corys which would help keep the gravel clean, and would help keep the waste down, but I wouldn't add the guppies.

 

also is 4 danios enough? do they need a bigger school? is that why they are chasing each other?

 

I have 3 pearl danios and they do fine so ur probably alright

 

Danios just normally play follow the leader ;D
Carol