Hi, I have an empty 20g that I would like to put freshwater fish in. I am thinking a combination of platies, guppies and cory's. Any recommendation of how many of each I should get in total? I will get same sex so no offspring will be in the tank. The tank will start out cycled as I will be taking some bio-max from my cycled fancy goldfish tank. How many should I start out with? and how long in between adding more? Should I add in one type of fish at a time or a little of each? Thanks so much, this will be my first time having fish other then fancy goldies.