Controlling guppy fry. Can i keep only male guppies?

There are lots of fish you can add that will keep baby guppies in line. Pretty much everything will eat them.

A lone female betta will wreck havoc on Guppy Fry and depending on the female she should be okay to keep with your guppies. Every now and then you'll get a ***** that wants to kill everything but not too often.
 
AquariaCentral.com